205-435: Ontology is the philosophical study of being. It is traditionally understood as the subdiscipline of metaphysics focused on the most general features of reality . As one of the most fundamental concepts, being encompasses all of reality and every entity within it. To articulate the basic structure of being, ontology examines what all things have in common. It also investigates how they can be grouped into basic types, such as
410-448: A binary black hole . A second gravitational wave was detected on 26 December 2015 and additional observations should continue but gravitational waves require extremely sensitive instruments. The combination of observations made using electromagnetic radiation, neutrinos or gravitational waves and other complementary information, is known as multi-messenger astronomy . One of the oldest fields in astronomy, and in all of science,
615-400: A conceptual scheme of a particular domain, such as the ontology of genes . In this context, an inventory is a comprehensive list of elements. A conceptual scheme is a framework of the key concepts and their relationships. Ontology is closely related to metaphysics but the exact relation of these two disciplines is disputed. A traditionally influential characterization asserts that ontology
820-745: A system of 12 categories , divided into the four classes: quantity, quality, relation, and modality. More recent theories of categories were proposed by C. S. Peirce , Edmund Husserl , Samuel Alexander , Roderick Chisholm , and E. J. Lowe . Many philosophers rely on the contrast between concrete and abstract objects . According to a common view, concrete objects, like rocks, trees, and human beings, exist in space and time, undergo changes, and impact each other as cause and effect. They contrast with abstract objects, like numbers and sets , which do not exist in space and time, are immutable, and do not engage in causal relations. Particulars are individual entities and include both concrete objects, like Aristotle,
1025-437: A book is made up of two covers and the pages between them. Each of these components is itself constituted of smaller parts, like molecules , atoms , and elementary particles . Mereology studies the relation between parts and wholes. One position in mereology says that every collection of entities forms a whole. According to another view, this is only the case for collections that fulfill certain requirements, for instance, that
1230-432: A bundle that includes the properties yellow, sour, and round. According to traditional bundle theory, the bundled properties are universals, meaning that the same property may belong to several different bundles. According to trope bundle theory, properties are particular entities that belong to a single bundle. Some ontologies focus not on distinct objects but on interrelatedness. According to relationalism, all of reality
1435-572: A comprehensive inventory of reality in which every entity belongs to exactly one category. Some philosophers, like Aristotle , say that entities belonging to different categories exist in distinct ways. Others, like John Duns Scotus , insist that there are no differences in the mode of being, meaning that everything exists in the same way . A related dispute is whether some entities have a higher degree of being than others, an idea already found in Plato 's work. The more common view in contemporary philosophy
1640-502: A different sense, for example, as abstract or fictional objects. Scientific realists say that the scientific description of the world is an accurate representation of reality. It is of particular relevance in regard to things that cannot be directly observed by humans but are assumed to exist by scientific theories, like electrons, forces, and laws of nature. Scientific anti-realism says that scientific theories are not descriptions of reality but instruments to predict observations and
1845-562: A few milliseconds to thousands of seconds before fading away. Only 10% of gamma-ray sources are non-transient sources. These steady gamma-ray emitters include pulsars, neutron stars , and black hole candidates such as active galactic nuclei. In addition to electromagnetic radiation, a few other events originating from great distances may be observed from the Earth. In neutrino astronomy , astronomers use heavily shielded underground facilities such as SAGE , GALLEX , and Kamioka II/III for
2050-400: A fire, is always followed by another phenomenon, like a feeling of pain. According to nomic regularity theories, regularities manifest as laws of nature studied by science. Counterfactual theories focus not on regularities but on how effects depend on their causes. They state that effects owe their existence to the cause and would not occur without them. According to primitivism, causation
2255-414: A gradual continuum. The word metaphysics has its origin in the ancient Greek words metá ( μετά , meaning ' after ' , ' above ' , and ' beyond' ' ) and phusiká ( φυσικά ), as a short form of ta metá ta phusiká , meaning ' what comes after the physics ' . This is often interpreted to mean that metaphysics discusses topics that, due to their generality and comprehensiveness, lie beyond
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#17327838804582460-422: A higher degree of existence than matter, which can only imperfectly reflect Platonic forms. Another key concern in metaphysics is the division of entities into distinct groups based on underlying features they share. Theories of categories provide a system of the most fundamental kinds or the highest genera of being by establishing a comprehensive inventory of everything. One of the earliest theories of categories
2665-568: A key role in ethics regarding the moral responsibility people have for what they do. Identity is a relation that every entity has to itself as a form of sameness. It refers to numerical identity when the very same entity is involved, as in the statement "the morning star is the evening star " (both are the planet Venus ). In a slightly different sense, it encompasses qualitative identity, also called exact similarity and indiscernibility , which occurs when two distinct entities are exactly alike, such as perfect identical twins. The principle of
2870-475: A long history in metaphysics, meta-metaphysics has only recently developed into a systematic field of inquiry. Metaphysicians often regard existence or being as one of the most basic and general concepts. To exist means to form part of reality , distinguishing real entities from imaginary ones. According to the orthodox view, existence is a property of properties: if an entity exists then its properties are instantiated. A different position states that existence
3075-411: A major subfield of applied ontology, studies social kinds, like money , gender , society , and language . It aims to determine the nature and essential features of these concepts while also examining their mode of existence. According to a common view, social kinds are useful constructions to describe the complexities of social life. This means that they are not pure fictions but, at the same time, lack
3280-552: A model allows astronomers to select between several alternative or conflicting models. Theorists also modify existing models to take into account new observations. In some cases, a large amount of observational data that is inconsistent with a model may lead to abandoning it largely or completely, as for geocentric theory , the existence of luminiferous aether , and the steady-state model of cosmic evolution. Phenomena modeled by theoretical astronomers include: Modern theoretical astronomy reflects dramatic advances in observation since
3485-671: A number of important astronomers. Richard of Wallingford (1292–1336) made major contributions to astronomy and horology , including the invention of the first astronomical clock, the Rectangulus which allowed for the measurement of angles between planets and other astronomical bodies, as well as an equatorium called the Albion which could be used for astronomical calculations such as lunar , solar and planetary longitudes and could predict eclipses . Nicole Oresme (1320–1382) and Jean Buridan (1300–1361) first discussed evidence for
3690-541: A person thinks about the Loch Ness Monster then the Loch Ness Monster is the intentional object of this thought . People can think about existing and non-existing objects. This makes it difficult to assess the ontological status of intentional objects . Ontological dependence is a relation between entities. An entity depends ontologically on another entity if the first entity cannot exist without
3895-445: A preliminary discipline that provides a complete inventory of reality while metaphysics examines the features and structure of the entities in this inventory. Another conception says that metaphysics is about real being while ontology examines possible being or the concept of being. It is not universally accepted that there is a clear boundary between metaphysics and ontology. Some philosophers use both terms as synonyms. The etymology of
4100-479: A priori methods have been the dominant approach. They rely on rational intuition and abstract reasoning from general principles rather than sensory experience . A posteriori approaches, by contrast, ground metaphysical theories in empirical observations and scientific theories. Some metaphysicians incorporate perspectives from fields such as physics , psychology , linguistics , and history into their inquiry. The two approaches are not mutually exclusive: it
4305-475: A priori reasoning and view metaphysics as a practice continuous with the empirical sciences that generalizes their insights while making their underlying assumptions explicit. This approach is known as naturalized metaphysics and is closely associated with the work of Willard Van Orman Quine . He relies on the idea that true sentences from the sciences and other fields have ontological commitments , that is, they imply that certain entities exist. For example, if
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#17327838804584510-522: A real part of objects. Relational ontologies are common in certain forms of nominalism that reject the existence of universal properties. Hierarchical ontologies state that the world is organized into levels. Entities on all levels are real but low-level entities are more fundamental than high-level entities. This means that they can exist without high-level entities while high-level entities cannot exist without low-level entities. One hierarchical ontology says that elementary particles are more fundamental than
4715-578: A repeating cycle known as a saros . Following the Babylonians, significant advances in astronomy were made in ancient Greece and the Hellenistic world. Greek astronomy is characterized from the start by seeking a rational, physical explanation for celestial phenomena. In the 3rd century BC, Aristarchus of Samos estimated the size and distance of the Moon and Sun , and he proposed a model of
4920-465: A single cloud is an overlay of countless clouds, one for each cloud-like collection of water droplets. Mereological moderatists hold that certain conditions must be met for a group of entities to compose a whole, for example, that the entities touch one another. Mereological nihilists reject the idea of wholes altogether, claiming that there are no clouds or tables but only particles that are arranged cloud-wise or table-wise. A related mereological problem
5125-401: A situation relevant to an ontological issue and then employing counterfactual thinking to assess the consequences of this situation. For example, some ontologists examine the relation between mind and matter by imagining creatures identical to humans but without consciousness . Metaphysics Metaphysics is the branch of philosophy that examines the basic structure of reality . It
5330-400: A slightly different sense, monism contrasts with pluralism as a view not about the number of basic types but the number of entities. In this sense, monism is the controversial position that only a single all-encompassing entity exists in all of reality. Pluralism is more commonly accepted and says that several distinct entities exist. The historically influential substance-attribute ontology
5535-402: A statement is possibly true if it is true in at least one possible world, whereas it is necessarily true if it is true in all possible worlds. Modal realists argue that possible worlds exist as concrete entities in the same sense as the actual world, with the main difference being that the actual world is the world we live in while other possible worlds are inhabited by counterparts . This view
5740-608: A substantial amount of work in the realms of theoretical and observational physics. Some areas of study for astrophysicists include their attempts to determine the properties of dark matter , dark energy , and black holes ; whether or not time travel is possible, wormholes can form, or the multiverse exists; and the origin and ultimate fate of the universe . Topics also studied by theoretical astrophysicists include Solar System formation and evolution ; stellar dynamics and evolution ; galaxy formation and evolution ; magnetohydrodynamics ; large-scale structure of matter in
5945-464: A substratum, also called bare particular , together with various properties. The substratum confers individuality to the particular while the properties express its qualitative features or what it is like. This approach is rejected by bundle theorists , who state that particulars are only bundles of properties without an underlying substratum. Some bundle theorists include in the bundle an individual essence, called haecceity , to ensure that each bundle
6150-461: A term from German philosopher Gottfried Wilhelm Leibniz 's theodicy , many metaphysicians use the concept of possible worlds to analyze the meaning and ontological ramifications of modal statements. A possible world is a complete and consistent way the totality of things could have been. For example, the dinosaurs were wiped out in the actual world but there are possible worlds in which they are still alive. According to possible world semantics,
6355-467: A theory of reality but as a game governed by rules of string manipulation. Modal realism is the theory that in addition to the actual world, there are countless possible worlds as real and concrete as the actual world. The primary difference is that the actual world is inhabited by us while other possible worlds are inhabited by our counterparts . Modal anti-realists reject this view and argue that possible worlds do not have concrete reality but exist in
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6560-499: A tree, a car, and a planet. They have causal powers and can affect each other, like when a car hits a tree and both are deformed in the process. Abstract objects, by contrast, are outside space and time, such as the number 7 and the set of integers . They lack causal powers and do not undergo changes. The existence and nature of abstract objects remain subjects of philosophical debate. Concrete objects encountered in everyday life are complex entities composed of various parts. For example,
6765-401: A truthmaker for the statement "a tomato is red". Based on this observation, it is possible to pursue metaphysical research by asking what the truthmakers of statements are, with different areas of metaphysics being dedicated to different types of statements. According to this view, modal metaphysics asks what makes statements about what is possible and necessary true while the metaphysics of time
6970-621: A unified dimension rather than as independent dimensions. Empirically focused metaphysicians often rely on scientific theories to ground their theories about the nature of reality in empirical observations. Similar issues arise in the social sciences where metaphysicians investigate their basic concepts and analyze their metaphysical implications. This includes questions like whether social facts emerge from non-social facts, whether social groups and institutions have mind-independent existence, and how they persist through time. Metaphysical assumptions and topics in psychology and psychiatry include
7175-427: Is visible light , or more generally electromagnetic radiation . Observational astronomy may be categorized according to the corresponding region of the electromagnetic spectrum on which the observations are made. Some parts of the spectrum can be observed from the Earth's surface, while other parts are only observable from either high altitudes or outside the Earth's atmosphere. Specific information on these subfields
7380-586: Is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics , physics , and chemistry in order to explain their origin and their overall evolution . Objects of interest include planets , moons , stars , nebulae , galaxies , meteoroids , asteroids , and comets . Relevant phenomena include supernova explosions, gamma ray bursts , quasars , blazars , pulsars , and cosmic microwave background radiation . More generally, astronomy studies everything that originates beyond Earth's atmosphere . Cosmology
7585-399: Is a basic concept that cannot be analyzed in terms of non-causal concepts, such as regularities or dependence relations. One form of primitivism identifies causal powers inherent in entities as the underlying mechanism. Eliminativists reject the above theories by holding that there is no causation. Mind encompasses phenomena like thinking , perceiving , feeling , and desiring as well as
7790-590: Is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky . These include the Egyptians , Babylonians , Greeks , Indians , Chinese , Maya , and many ancient indigenous peoples of the Americas . In the past, astronomy included disciplines as diverse as astrometry , celestial navigation , observational astronomy , and
7995-555: Is a comprehensive framework for the standardized representation of gene-related information across species and databases. Formal ontology is the study of objects in general while focusing on their abstract structures and features. It divides objects into different categories based on the forms they exemplify. Formal ontologists often rely on the tools of formal logic to express their findings in an abstract and general manner. Formal ontology contrasts with material ontology, which distinguishes between different areas of objects and examines
8200-435: Is a fundamental aspect of reality, meaning that besides facts about what is the case, there are additional facts about what could or must be the case. A different view argues that modal truths are not about an independent aspect of reality but can be reduced to non-modal characteristics, for example, to facts about what properties or linguistic descriptions are compatible with each other or to fictional statements . Borrowing
8405-403: Is a polycategorical theory. It says that reality is at its most fundamental level made up of unanalyzable substances that are characterized by universals, such as the properties an individual substance has or relations that exist between substances. The closely related to substratum theory says that each concrete object is made up of properties and a substratum. The difference is that the substratum
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8610-521: Is a property of individuals, meaning that it is similar to other properties, such as shape or size. It is controversial whether all entities have this property. According to Alexius Meinong , there are nonexistent objects , including merely possible objects like Santa Claus and Pegasus . A related question is whether existence is the same for all entities or whether there are different modes or degrees of existence. For instance, Plato held that Platonic forms , which are perfect and immutable ideas, have
8815-410: Is a related method in phenomenological ontology that aims to identify the essential features of different types of objects. Phenomenologists start by imagining an example of the investigated type. They proceed by varying the imagined features to determine which ones cannot be changed, meaning they are essential. The transcendental method begins with a simple observation that a certain entity exists. In
9020-427: Is a relation, as in " Kathmandu is a city" and "Kathmandu is east of New Delhi ". Relations are often divided into internal and external relations . Internal relations depend only on the properties of the objects they connect, like the relation of resemblance . External relations express characteristics that go beyond what the connected objects are like, such as spatial relations. Substances play an important role in
9225-425: Is a subdiscipline of metaphysics. According to this view, metaphysics is the study of various aspects of fundamental reality, whereas ontology restricts itself to the most general features of reality. This view sees ontology as general metaphysics, which is to be distinguished from special metaphysics focused on more specific subject matters, like God , mind , and value . A different conception understands ontology as
9430-442: Is a well-known principle that gives preference to simple theories, in particular, those that assume that few entities exist. Other principles consider explanatory power , theoretical usefulness, and proximity to established beliefs. Despite its status as one of the main branches of philosophy, metaphysics has received numerous criticisms questioning its legitimacy as a field of inquiry. One criticism argues that metaphysical inquiry
9635-584: Is absorbed by the Earth's atmosphere, requiring observations at these wavelengths to be performed from the upper atmosphere or from space. Ultraviolet astronomy is best suited to the study of thermal radiation and spectral emission lines from hot blue stars ( OB stars ) that are very bright in this wave band. This includes the blue stars in other galaxies, which have been the targets of several ultraviolet surveys. Other objects commonly observed in ultraviolet light include planetary nebulae , supernova remnants , and active galactic nuclei. However, as ultraviolet light
9840-595: Is also believed that the ruins at Great Zimbabwe and Timbuktu may have housed astronomical observatories. In Post-classical West Africa , Astronomers studied the movement of stars and relation to seasons, crafting charts of the heavens as well as precise diagrams of orbits of the other planets based on complex mathematical calculations. Songhai historian Mahmud Kati documented a meteor shower in August 1583. Europeans had previously believed that there had been no astronomical observation in sub-Saharan Africa during
10045-583: Is an inseparable part of the discipline of astrobiology. Astrobiology concerns itself with interpretation of existing scientific data , and although speculation is entertained to give context, astrobiology concerns itself primarily with hypotheses that fit firmly into existing scientific theories . This interdisciplinary field encompasses research on the origin of planetary systems , origins of organic compounds in space , rock-water-carbon interactions, abiogenesis on Earth, planetary habitability , research on biosignatures for life detection, and studies on
10250-572: Is between analytic and speculative ontology. Analytic ontology examines the types and categories of being to determine what kinds of things could exist and what features they would have. Speculative ontology aims to determine which entities actually exist, for example, whether there are numbers or whether time is an illusion. Metaontology studies the underlying concepts, assumptions, and methods of ontology. Unlike other forms of ontology, it does not ask "what exists" but "what does it mean for something to exist" and "how can people determine what exists". It
10455-703: Is closely related to fundamental ontology , an approach developed by philosopher Martin Heidegger that seeks to uncover the meaning of being. The term realism is used for various theories that affirm that some kind of phenomenon is real or has mind-independent existence. Ontological realism is the view that there are objective facts about what exists and what the nature and categories of being are. Ontological realists do not make claims about what those facts are, for example, whether elementary particles exist. They merely state that there are mind-independent facts that determine which ontological theories are true. This idea
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#173278388045810660-440: Is controversial and various alternatives have been suggested, for example, that possible worlds only exist as abstract objects or are similar to stories told in works of fiction . Space and time are dimensions that entities occupy. Spacetime realists state that space and time are fundamental aspects of reality and exist independently of the human mind. Spacetime idealists, by contrast, hold that space and time are constructs of
10865-476: Is controversial whether a more substantial analysis of the concept or meaning of being is possible. One proposal understands being as a property possessed by every entity. Critics argue that a thing without being cannot have properties. This means that properties presuppose being and cannot explain it. Another suggestion is that all beings share a set of essential features. According to the Eleatic principle , "power
11070-435: Is denied by ontological anti-realists, also called ontological deflationists, who say that there are no substantive facts one way or the other. According to philosopher Rudolf Carnap , for example, ontological statements are relative to language and depend on the ontological framework of the speaker. This means that there are no framework-independent ontological facts since different frameworks provide different views while there
11275-401: Is determined. Hard determinists infer from this that there is no free will, whereas libertarians conclude that determinism must be false. Compatibilists offer a third perspective, arguing that determinism and free will do not exclude each other, for instance, because a person can still act in tune with their motivation and choices even if they are determined by other forces. Free will plays
11480-400: Is divided into subdisciplines based on the perspective they take. Metaphysical cosmology examines changeable things and investigates how they are connected to form a world as a totality extending through space and time. Rational psychology focuses on metaphysical foundations and problems concerning the mind, such as its relation to matter and the freedom of the will. Natural theology studies
11685-427: Is easily absorbed by interstellar dust , an adjustment of ultraviolet measurements is necessary. X-ray astronomy uses X-ray wavelengths . Typically, X-ray radiation is produced by synchrotron emission (the result of electrons orbiting magnetic field lines), thermal emission from thin gases above 10 (10 million) kelvins , and thermal emission from thick gases above 10 Kelvin. Since X-rays are absorbed by
11890-427: Is essential if an entity must have it; it is accidental if the entity can exist without it. For instance, having three sides is an essential property of a triangle, whereas being red is an accidental property. Relations are ways how two or more entities stand to one another. Unlike properties, they apply to several entities and characterize them as a group. For example, being a city is a property while being east of
12095-414: Is founded on the detection and analysis of infrared radiation, wavelengths longer than red light and outside the range of our vision. The infrared spectrum is useful for studying objects that are too cold to radiate visible light, such as planets, circumstellar disks or nebulae whose light is blocked by dust. The longer wavelengths of infrared can penetrate clouds of dust that block visible light, allowing
12300-464: Is from these clouds that solar systems form. Studies in this field contribute to the understanding of the formation of the Solar System , Earth's origin and geology, abiogenesis , and the origin of climate and oceans. Astrobiology is an interdisciplinary scientific field concerned with the origins , early evolution , distribution, and future of life in the universe . Astrobiology considers
12505-436: Is fundamentally neither material nor mental and suggest that matter and mind are both derivative phenomena. A key aspect of the mind–body problem is the hard problem of consciousness or how to explain that physical systems like brains can produce phenomenal consciousness. The status of free will as the ability of a person to choose their actions is a central aspect of the mind–body problem. Metaphysicians are interested in
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#173278388045812710-416: Is given below. Radio astronomy uses radiation with wavelengths greater than approximately one millimeter, outside the visible range. Radio astronomy is different from most other forms of observational astronomy in that the observed radio waves can be treated as waves rather than as discrete photons . Hence, it is relatively easier to measure both the amplitude and phase of radio waves, whereas this
12915-420: Is impossible because humans lack the cognitive capacities needed to access the ultimate nature of reality. This line of thought leads to skepticism about the possibility of metaphysical knowledge. Empiricists often follow this idea, like Hume, who argued that there is no good source of metaphysical knowledge since metaphysics lies outside the field of empirical knowledge and relies on dubious intuitions about
13120-434: Is interested in the truthmakers of temporal statements about the past, present, and future. A closely related topic concerns the nature of truth. Theories of truth aim to determine this nature and include correspondence , coherence , pragmatic , semantic , and deflationary theories . Metaphysicians employ a variety of methods to develop metaphysical theories and formulate arguments for and against them. Traditionally,
13325-468: Is made up of only one kind. According to idealism , everything is mental, including physical objects, which may be understood as ideas or perceptions of conscious minds. Materialists, by contrast, state that all reality is at its core material. Some deny that mind exists but the more common approach is to explain mind in terms of certain aspects of matter, such as brain states, behavioral dispositions , or functional roles. Neutral monists argue that reality
13530-600: Is material. This means that mental phenomena, such as beliefs, emotions, and consciousness, either do not exist or exist as aspects of matter, like brain states. Idealists take the converse perspective, arguing that everything is mental. They may understand physical phenomena, like rocks, trees, and planets, as ideas or perceptions of conscious minds. Neutral monism occupies a middle ground by saying that both mind and matter are derivative phenomena. Dualists state that mind and matter exist as independent principles, either as distinct substances or different types of properties . In
13735-454: Is necessary that three plus two equals five". Possibility and necessity contrast with actuality, which describes what is the case, as in " Doha is the capital of Qatar ". Ontologists often use the concept of possible worlds to analyze possibility and necessity. A possible world is a complete and consistent way how things could have been. For example, Haruki Murakami was born in 1949 in the actual world but there are possible worlds in which he
13940-419: Is no consensus about the validity of these criticisms and whether they affect metaphysics as a whole or only certain issues or approaches in it. For example, it could be the case that certain metaphysical disputes are merely verbal while others are substantive. Metaphysics is related to many fields of inquiry by investigating their basic concepts and relation to the fundamental structure of reality. For example,
14145-453: Is no objectively right or wrong framework. In a more narrow sense, realism refers to the existence of certain types of entities. Realists about universals say that universals have mind-independent existence. According to Platonic realists , universals exist not only independent of the mind but also independent of particular objects that exemplify them. This means that the universal red could exist by itself even if there were no red objects in
14350-441: Is no single standard method; the diverse approaches are studied by metaontology . Conceptual analysis is a method to understand ontological concepts and clarify their meaning. It proceeds by analyzing their component parts and the necessary and sufficient conditions under which a concept applies to an entity. This information can help ontologists decide whether a certain type of entity, such as numbers, exists. Eidetic variation
14555-645: Is not as easily done at shorter wavelengths. Although some radio waves are emitted directly by astronomical objects, a product of thermal emission , most of the radio emission that is observed is the result of synchrotron radiation , which is produced when electrons orbit magnetic fields . Additionally, a number of spectral lines produced by interstellar gas , notably the hydrogen spectral line at 21 cm, are observable at radio wavelengths. A wide variety of other objects are observable at radio wavelengths, including supernovae , interstellar gas, pulsars , and active galactic nuclei . Infrared astronomy
14760-410: Is not characterized by properties: it is a featureless or bare particular that merely supports the properties. Various alternative ontological theories have been proposed that deny the role of substances as the foundational building blocks of reality. Stuff ontologies say that the world is not populated by distinct entities but by continuous stuff that fills space. This stuff may take various forms and
14965-399: Is often conceived as infinitely divisible. According to process ontology , processes or events are the fundamental entities. This view usually emphasizes that nothing in reality is static, meaning that being is dynamic and characterized by constant change. Bundle theories state that there are no regular objects but only bundles of co-present properties. For example, a lemon may be understood as
15170-475: Is one of the few sciences in which amateurs play an active role . This is especially true for the discovery and observation of transient events . Amateur astronomers have helped with many important discoveries, such as finding new comets. Astronomy (from the Greek ἀστρονομία from ἄστρον astron , "star" and -νομία -nomia from νόμος nomos , "law" or "culture") means "law of the stars" (or "culture of
15375-411: Is one of the oldest branches of philosophy . The precise nature of metaphysics is disputed and its characterization has changed in the course of history. Some approaches see metaphysics as a unified field and give a wide-sweeping definition by understanding it as the study of "fundamental questions about the nature of reality" or as an inquiry into the essences of things. Another approach doubts that
15580-424: Is only one fundamental category, meaning that every single entity belongs to the same universal class. For example, some forms of nominalism state that only concrete particulars exist while some forms of bundle theory state that only properties exist. Polycategorical theories, by contrast, hold that there is more than one basic category, meaning that entities are divided into two or more fundamental classes. They take
15785-408: Is opposed by so-called serious metaphysicians , who contend that metaphysical disputes are about substantial features of the underlying structure of reality. A closely related debate between ontological realists and anti-realists concerns the question of whether there are any objective facts that determine which metaphysical theories are true. A different criticism, formulated by pragmatists , sees
15990-457: Is possible to combine elements from both. The method a metaphysician chooses often depends on their understanding of the nature of metaphysics, for example, whether they see it as an inquiry into the mind-independent structure of reality, as metaphysical realists claim, or the principles underlying thought and experience, as some metaphysical anti-realists contend. A priori approaches often rely on intuitions—non-inferential impressions about
16195-459: Is present but not the others. According to perdurantists, change means that an earlier part exhibits different qualities than a later part. When a tree loses its leaves, for instance, there is an earlier temporal part with leaves and a later temporal part without leaves. Differential ontology is a poststructuralist approach interested in the relation between the concepts of identity and difference . It says that traditional ontology sees identity as
16400-448: Is rejected by probabilistic theories , which claim that the cause merely increases the probability that the effect occurs. This view can explain that smoking causes cancer even though this does not happen in every single case. The regularity theory of causation , inspired by David Hume 's philosophy, states that causation is nothing but a constant conjunction in which the mind apprehends that one phenomenon, like putting one's hand in
16605-505: Is relational at its most fundamental level. Ontic structural realism agrees with this basic idea and focuses on how these relations form complex structures. Some structural realists state that there is nothing but relations, meaning that individual objects do not exist. Others say that individual objects exist but depend on the structures in which they participate. Fact ontologies present a different approach by focusing on how entities belonging to different categories come together to constitute
16810-418: Is studied by mereology . The problem of the many is a philosophical question about the conditions under which several individual things compose a larger whole. For example, a cloud is made up of many droplets without a clear boundary, raising the question of which droplets form part of the cloud. According to mereological universalists, every collection of entities forms a whole. This means that what seems to be
17015-441: Is that a thing either exists or not with no intermediary states or degrees. The relation between being and non-being is a frequent topic in ontology. Influential issues include the status of nonexistent objects and why there is something rather than nothing . A central distinction in ontology is between particular and universal entities. Particulars, also called individuals , are unique, non-repeatable entities, like Socrates ,
17220-479: Is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects , rather than their positions or motions in space". Among the objects studied are the Sun , other stars , galaxies , extrasolar planets , the interstellar medium and the cosmic microwave background . Their emissions are examined across all parts of the electromagnetic spectrum , and
17425-406: Is the cause and the spill is the effect. Besides the single-case causation between particulars in this example, there is also general-case causation expressed in statements such as "smoking causes cancer". The term agent causation is used when people and their actions cause something. Causation is usually interpreted deterministically, meaning that a cause always brings about its effect. This view
17630-415: Is the mark of being", meaning that only entities with causal influence truly exist. A controversial proposal by philosopher George Berkeley suggests that all existence is mental. He expressed this immaterialism in his slogan "to be is to be perceived". Depending on the context, the term being is sometimes used with a more limited meaning to refer only to certain aspects of reality. In one sense, being
17835-502: Is the measurement of the positions of celestial objects. Historically, accurate knowledge of the positions of the Sun, Moon, planets and stars has been essential in celestial navigation (the use of celestial objects to guide navigation) and in the making of calendars . Careful measurement of the positions of the planets has led to a solid understanding of gravitational perturbations , and an ability to determine past and future positions of
18040-417: Is the most basic inquiry upon which all other branches of philosophy depend in some way. Metaphysics is traditionally understood as a study of mind-independent features of reality. Starting with Immanuel Kant 's critical philosophy , an alternative conception gained prominence that focuses on conceptual schemes rather than external reality. Kant distinguishes transcendent metaphysics, which aims to describe
18245-518: Is the relation between a ground and the facts it explains. An ontological commitment of a person or a theory is an entity that exists according to them. For instance, a person who believes in God has an ontological commitment to God . Ontological commitments can be used to analyze which ontologies people explicitly defend or implicitly assume. They play a central role in contemporary metaphysics when trying to decide between competing theories. For example,
18450-429: Is traditionally seen as the study of mind-independent features of the world, but some theorists view it as an inquiry into the fundamental categories of human understanding. Some philosophers, including Aristotle , designate metaphysics as first philosophy to suggest that it is more fundamental than other forms of philosophical inquiry. Metaphysics encompasses a wide range of general and abstract topics. It investigates
18655-566: Is unchanging and permanent, in contrast to becoming, which implies change. Another contrast is between being, as what truly exists, and phenomena , as what appears to exist. In some contexts, being expresses the fact that something is while essence expresses its qualities or what it is like. Ontologists often divide being into fundamental classes or highest kinds, called categories of being . Proposed categories include substance, property , relation , state of affairs , and event . They can be used to provide systems of categories, which offer
18860-401: Is unique. Another proposal for concrete particulars is that they are individuated by their space-time location. Concrete particulars encountered in everyday life, like rocks, tables, and organisms, are complex entities composed of various parts. For example, a table is made up of a tabletop and legs, each of which is itself made up of countless particles. The relation between parts and wholes
19065-465: Is whether there are simple entities that have no parts, as atomists claim, or whether everything can be endlessly subdivided into smaller parts, as continuum theorists contend. Universals are general entities, encompassing both properties and relations , that express what particulars are like and how they resemble one another. They are repeatable, meaning that they are not limited to a unique existent but can be instantiated by different particulars at
19270-484: The Compton Gamma Ray Observatory or by specialized telescopes called atmospheric Cherenkov telescopes . The Cherenkov telescopes do not detect the gamma rays directly but instead detect the flashes of visible light produced when gamma rays are absorbed by the Earth's atmosphere. Most gamma-ray emitting sources are actually gamma-ray bursts , objects which only produce gamma radiation for
19475-524: The Earth's atmosphere , all X-ray observations must be performed from high-altitude balloons , rockets , or X-ray astronomy satellites . Notable X-ray sources include X-ray binaries , pulsars , supernova remnants , elliptical galaxies , clusters of galaxies , and active galactic nuclei . Gamma ray astronomy observes astronomical objects at the shortest wavelengths of the electromagnetic spectrum. Gamma rays may be observed directly by satellites such as
19680-977: The Milky Way , as its own group of stars was only proven in the 20th century, along with the existence of "external" galaxies. The observed recession of those galaxies led to the discovery of the expansion of the Universe . In 1919, when the Hooker Telescope was completed, the prevailing view was that the universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope, Edwin Hubble identified Cepheid variables in several spiral nebulae and in 1922–1923 proved conclusively that Andromeda Nebula and Triangulum among others, were entire galaxies outside our own, thus proving that
19885-794: The Muslim world by the early 9th century. In 964, the Andromeda Galaxy , the largest galaxy in the Local Group , was described by the Persian Muslim astronomer Abd al-Rahman al-Sufi in his Book of Fixed Stars . The SN 1006 supernova , the brightest apparent magnitude stellar event in recorded history, was observed by the Egyptian Arabic astronomer Ali ibn Ridwan and Chinese astronomers in 1006. Iranian scholar Al-Biruni observed that, contrary to Ptolemy ,
20090-455: The Quine–Putnam indispensability argument defends mathematical Platonism , asserting that numbers exist because the best scientific theories are ontologically committed to numbers. Possibility and necessity are further topics in ontology. Possibility describes what can be the case, as in "it is possible that extraterrestrial life exists". Necessity describes what must be the case, as in "it
20295-561: The Renaissance , Nicolaus Copernicus proposed a heliocentric model of the solar system. His work was defended by Galileo Galilei and expanded upon by Johannes Kepler . Kepler was the first to devise a system that correctly described the details of the motion of the planets around the Sun. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was Isaac Newton , with his invention of celestial dynamics and his law of gravitation , who finally explained
20500-561: The Solar System where the Earth and planets rotated around the Sun, now called the heliocentric model. In the 2nd century BC, Hipparchus discovered precession , calculated the size and distance of the Moon and invented the earliest known astronomical devices such as the astrolabe . Hipparchus also created a comprehensive catalog of 1020 stars, and most of the constellations of the northern hemisphere derive from Greek astronomy. The Antikythera mechanism ( c. 150 –80 BC)
20705-619: The Taj Mahal , and Mars . Universals are general, repeatable entities, like the color green , the form circularity , and the virtue courage . Universals express aspects or features shared by particulars. For example, Mount Everest and Mount Fuji are particulars characterized by the universal mountain . Universals can take the form of properties or relations. Properties describe the characteristics of things. They are features or qualities possessed by an entity. Properties are often divided into essential and accidental properties . A property
20910-510: The Upanishads in ancient India , Daoism in ancient China , and pre-Socratic philosophy in ancient Greece . During the subsequent medieval period in the West, discussions about the nature of universals were influenced by the philosophies of Plato and Aristotle. The modern period saw the emergence of various comprehensive systems of metaphysics, many of which embraced idealism . In
21115-638: The Vaisheshika school, distinguishes between six categories: substance , quality, motion, universal, individuator, and inherence. Immanuel Kant 's transcendental idealism includes a system of twelve categories, which Kant saw as pure concepts of understanding. They are subdivided into four classes: quantity, quality, relation, and modality. In more recent philosophy, theories of categories were developed by C. S. Peirce , Edmund Husserl , Samuel Alexander , Roderick Chisholm , and E. J. Lowe . The dispute between constituent and relational ontologies concerns
21320-501: The ancient period with speculations about the nature of being and the source of the universe, including ancient Indian , Chinese , and Greek philosophy . In the modern period, philosophers conceived ontology as a distinct academic discipline and coined its name. Ontology is the study of being. It is the branch of philosophy that investigates the nature of existence , the features all entities have in common, and how they are divided into basic categories of being . It aims to discover
21525-585: The categories of particulars and universals . Particulars are unique, non-repeatable entities, like the person Socrates . Universals are general, repeatable entities, like the color green . Another contrast is between concrete objects existing in space and time, like a tree, and abstract objects existing outside space and time, like the number 7. Systems of categories aim to provide a comprehensive inventory of reality, employing categories such as substance , property , relation , state of affairs , and event . Ontologists disagree about which entities exist on
21730-492: The concepts of space, time, and change , and their connection to causality and the laws of nature . Other topics include how mind and matter are related , whether everything in the world is predetermined , and whether there is free will . Metaphysicians use various methods to conduct their inquiry. Traditionally, they rely on rational intuitions and abstract reasoning but have more recently also included empirical approaches associated with scientific theories. Due to
21935-454: The history of philosophy , various ontological theories based on several fundamental categories have been proposed. One of the first theories of categories was suggested by Aristotle , whose system includes ten categories: substance, quantity , quality , relation, place, date, posture, state, action, and passion. An early influential system of categories in Indian philosophy, first proposed in
22140-427: The interstellar medium . The study of the abundance of elements and isotope ratios in Solar System objects, such as meteorites , is also called cosmochemistry , while the study of interstellar atoms and molecules and their interaction with radiation is sometimes called molecular astrophysics. The formation, atomic and chemical composition, evolution and fate of molecular gas clouds is of special interest, because it
22345-404: The social sciences . Applied ontology is of particular relevance to information and computer science , which develop conceptual frameworks of limited domains . These frameworks are used to store information in a structured way, such as a college database tracking academic activities. Ontology is relevant to the fields of logic , theology , and anthropology . The origins of ontology lie in
22550-442: The 1990s, including studies of the cosmic microwave background , distant supernovae and galaxy redshifts , which have led to the development of a standard model of cosmology . This model requires the universe to contain large amounts of dark matter and dark energy whose nature is currently not well understood, but the model gives detailed predictions that are in excellent agreement with many diverse observations. Astrophysics
22755-404: The 20th century, traditional metaphysics in general and idealism in particular faced various criticisms, which prompted new approaches to metaphysical inquiry. Metaphysics is the study of the most general features of reality , including existence , objects and their properties , possibility and necessity, space and time , change, causation , and the relation between matter and mind . It
22960-403: The Earth's atmosphere and of their physical and chemical properties", while "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, and dynamic processes of celestial objects and phenomena". In some cases, as in the introduction of the introductory textbook The Physical Universe by Frank Shu , "astronomy" may be used to describe the qualitative study of
23165-627: The Eiffel Tower, or a specific apple, and abstract objects, like the number 2 or a specific set in mathematics. Also called individuals , they are unique, non-repeatable entities and contrast with universals , like the color red, which can at the same time exist in several places and characterize several particulars. A widely held view is that particulars instantiate universals but are not themselves instantiated by something else, meaning that they exist in themselves while universals exist in something else. Substratum theory analyzes each particular as
23370-523: The English language through the Latin word metaphysica . The nature of metaphysics can also be characterized in relation to its main branches. An influential division from early modern philosophy distinguishes between general and special or specific metaphysics. General metaphysics, also called ontology , takes the widest perspective and studies the most fundamental aspects of being. It investigates
23575-513: The Rings , and people, like the Monkey King in the novel Journey to the West . Some philosophers say that fictional objects are abstract objects and exist outside space and time. Others understand them as artifacts that are created as the works of fiction are written. Intentional objects are entities that exist within mental states , like perceptions , beliefs , and desires . For example, if
23780-527: The Sun's apogee (highest point in the heavens) was mobile, not fixed. Some of the prominent Islamic (mostly Persian and Arab) astronomers who made significant contributions to the science include Al-Battani , Thebit , Abd al-Rahman al-Sufi , Biruni , Abū Ishāq Ibrāhīm al-Zarqālī , Al-Birjandi , and the astronomers of the Maragheh and Samarkand observatories. Astronomers during that time introduced many Arabic names now used for individual stars . It
23985-584: The Sun, the Moon and the stars rotating around it. This is known as the geocentric model of the Universe, or the Ptolemaic system , named after Ptolemy . A particularly important early development was the beginning of mathematical and scientific astronomy, which began among the Babylonians , who laid the foundations for the later astronomical traditions that developed in many other civilizations. The Babylonians discovered that lunar eclipses recurred in
24190-402: The abstract nature of its topic, metaphysics has received criticisms questioning the reliability of its methods and the meaningfulness of its theories. Metaphysics is relevant to many fields of inquiry that often implicitly rely on metaphysical concepts and assumptions. The roots of metaphysics lie in antiquity with speculations about the nature and origin of the universe, like those found in
24395-535: The age of the Universe and size of the Observable Universe. Theoretical astronomy led to speculations on the existence of objects such as black holes and neutron stars , which have been used to explain such observed phenomena as quasars , pulsars , blazars , and radio galaxies . Physical cosmology made huge advances during the 20th century. In the early 1900s the model of the Big Bang theory
24600-422: The analysis of concepts and experience , the use of intuitions and thought experiments , and the integration of findings from natural science . Formal ontology is the branch of ontology investigating the most abstract features of objects. Applied ontology employs ontological theories and principles to study entities belonging to a specific area. For example, social ontology examines basic concepts used in
24805-486: The atmosphere itself produces significant infrared emission. Consequently, infrared observatories have to be located in high, dry places on Earth or in space. Some molecules radiate strongly in the infrared. This allows the study of the chemistry of space; more specifically it can detect water in comets. Historically, optical astronomy, which has been also called visible light astronomy, is the oldest form of astronomy. Images of observations were originally drawn by hand. In
25010-430: The average person thinks about an issue. For example, common-sense philosophers have argued that mereological nihilism is false since it implies that commonly accepted things, like tables, do not exist. Conceptual analysis , a method particularly prominent in analytic philosophy , aims to decompose metaphysical concepts into component parts to clarify their meaning and identify essential relations. In phenomenology ,
25215-404: The concepts of truth , truth-bearer , and truthmaker to conduct their inquiry. Truth is a property of being in accord with reality. Truth-bearers are entities that can be true or false, such as linguistic statements and mental representations. A truthmaker of a statement is the entity whose existence makes the statement true. For example, the fact that a tomato exists and that it is red acts as
25420-768: The correctness of specific claims or general principles. For example, arguments for the A-theory of time , which states that time flows from the past through the present and into the future, often rely on pre-theoretical intuitions associated with the sense of the passage of time. Some approaches use intuitions to establish a small set of self-evident fundamental principles, known as axioms , and employ deductive reasoning to build complex metaphysical systems by drawing conclusions from these axioms. Intuition-based approaches can be combined with thought experiments , which help evoke and clarify intuitions by linking them to imagined situations. They use counterfactual thinking to assess
25625-408: The department is historically affiliated with a physics department, and many professional astronomers have physics rather than astronomy degrees. Some titles of the leading scientific journals in this field include The Astronomical Journal , The Astrophysical Journal , and Astronomy & Astrophysics . In early historic times, astronomy only consisted of the observation and predictions of
25830-474: The detection of neutrinos . The vast majority of the neutrinos streaming through the Earth originate from the Sun , but 24 neutrinos were also detected from supernova 1987A . Cosmic rays , which consist of very high energy particles (atomic nuclei) that can decay or be absorbed when they enter the Earth's atmosphere, result in a cascade of secondary particles which can be detected by current observatories. Some future neutrino detectors may also be sensitive to
26035-452: The different areas of metaphysics share a set of underlying features and provides instead a fine-grained characterization by listing all the main topics investigated by metaphysicians. Some definitions are descriptive by providing an account of what metaphysicians do while others are normative and prescribe what metaphysicians ought to do. Two historically influential definitions in ancient and medieval philosophy understand metaphysics as
26240-496: The divine and its role as the first cause. The scope of special metaphysics overlaps with other philosophical disciplines, making it unclear whether a topic belongs to it or to areas like philosophy of mind and theology . Applied metaphysics is a relatively young subdiscipline. It belongs to applied philosophy and studies the applications of metaphysics, both within philosophy and other fields of inquiry. In areas like ethics and philosophy of religion , it addresses topics like
26445-497: The entities in the collection touch one another. The problem of material constitution asks whether or in what sense a whole should be considered a new object in addition to the collection of parts composing it. Abstract objects are closely related to fictional and intentional objects . Fictional objects are entities invented in works of fiction . They can be things, like the One Ring in J. R. R. Tolkien 's book series The Lord of
26650-687: The fault of metaphysics not in its cognitive ambitions or the meaninglessness of its statements, but in its practical irrelevance and lack of usefulness. Martin Heidegger criticized traditional metaphysics, saying that it fails to distinguish between individual entities and being as their ontological ground. His attempt to reveal the underlying assumptions and limitations in the history of metaphysics to "overcome metaphysics" influenced Jacques Derrida 's method of deconstruction . Derrida employed this approach to criticize metaphysical texts for relying on opposing terms, like presence and absence, which he thought were inherently unstable and contradictory. There
26855-427: The features characteristic of a specific area. Examples are ideal spatial beings in the area of geometry and living beings in the area of biology. Descriptive ontology aims to articulate the conceptual scheme underlying how people ordinarily think about the world. Prescriptive ontology departs from common conceptions of the structure of reality and seeks to formulate a new and better conceptualization. Another contrast
27060-447: The features that all entities share and how entities can be divided into different categories . Categories are the most general kinds, such as substance, property, relation , and fact . Ontologists research which categories there are, how they depend on one another, and how they form a system of categories that provides a comprehensive classification of all entities. Special metaphysics considers being from more narrow perspectives and
27265-552: The following step, it studies the ontological repercussions of this observation by examining how it is possible or which conditions are required for this entity to exist. Another approach is based on intuitions in the form of non-inferential impressions about the correctness of general principles. These principles can be used as the foundation on which an ontological system is built and expanded using deductive reasoning . A further intuition-based method relies on thought experiments to evoke new intuitions. This happens by imagining
27470-407: The form of systems of categories, which list the highest genera of being to provide a comprehensive inventory of everything. The closely related discussion between monism and dualism is about the most fundamental types that make up reality. According to monism, there is only one kind of thing or substance on the most basic level. Materialism is an influential monist view; it says that everything
27675-485: The foundational building blocks of the world and characterize reality as a whole in its most general aspects. In this regard, ontology contrasts with individual sciences like biology and astronomy , which restrict themselves to a limited domain of entities, such as living entities and celestial phenomena. In some contexts, the term ontology refers not to the general study of being but to a specific ontological theory within this discipline. It can also mean an inventory or
27880-468: The fundamental structure of mind-independent reality. The concepts of possibility and necessity convey what can or must be the case, expressed in modal statements like "it is possible to find a cure for cancer" and "it is necessary that two plus two equals four". Modal metaphysics studies metaphysical problems surrounding possibility and necessity, for instance, why some modal statements are true while others are false. Some metaphysicians hold that modality
28085-427: The history of ontology as the particular entities that underlie and support properties and relations. They are often considered the fundamental building blocks of reality that can exist on their own, while entities like properties and relations cannot exist without substances. Substances persist through changes as they acquire or lose properties. For example, when a tomato ripens, it loses the property green and acquires
28290-404: The human mind, created to organize and make sense of reality. Spacetime absolutism or substantivalism understands spacetime as a distinct object, with some metaphysicians conceptualizing it as a container that holds all other entities within it. Spacetime relationism sees spacetime not as an object but as a network of relations between objects, such as the spatial relation of being next to and
28495-443: The indiscernibility of identicals is widely accepted and holds that numerically identical entities exactly resemble one another. The converse principle, known as identity of indiscernibles or Leibniz's Law, is more controversial and states that two entities are numerically identical if they exactly resemble one another. Another distinction is between synchronic and diachronic identity. Synchronic identity relates an entity to itself at
28700-415: The individual sciences by studying the most general and abstract aspects of reality. The individual sciences, by contrast, examine more specific and concrete features and restrict themselves to certain classes of entities, such as the focus on physical things in physics , living entities in biology , and cultures in anthropology . It is disputed to what extent this contrast is a strict dichotomy rather than
28905-588: The internal structure of concrete particular objects. Constituent ontologies say that objects have an internal structure with properties as their component parts. Bundle theories are an example of this position: they state that objects are bundles of properties. This view is rejected by relational ontologies, which say that objects have no internal structure, meaning that properties do not inhere in them but are externally related to them. According to one analogy, objects are like pin-cushions and properties are pins that can be stuck to objects and removed again without becoming
29110-414: The introduction of new technology, including the spectroscope and photography . Joseph von Fraunhofer discovered about 600 bands in the spectrum of the Sun in 1814–15, which, in 1859, Gustav Kirchhoff ascribed to the presence of different elements. Stars were proven to be similar to the Earth's own Sun, but with a wide range of temperatures , masses , and sizes. The existence of the Earth's galaxy,
29315-579: The late 19th century and most of the 20th century, images were made using photographic equipment. Modern images are made using digital detectors, particularly using charge-coupled devices (CCDs) and recorded on modern medium. Although visible light itself extends from approximately 4000 Å to 7000 Å (400 nm to 700 nm), that same equipment can be used to observe some near-ultraviolet and near-infrared radiation. Ultraviolet astronomy employs ultraviolet wavelengths between approximately 100 and 3200 Å (10 to 320 nm). Light at those wavelengths
29520-601: The level at which it exists. The ontological theories of endurantism and perdurantism aim to explain how material objects persist through time. Endurantism is the view that material objects are three-dimensional entities that travel through time while being fully present in each moment. They remain the same even when they gain or lose properties as they change. Perdurantism is the view that material objects are four-dimensional entities that extend not just through space but also through time. This means that they are composed of temporal parts and, at any moment, only one part of them
29725-417: The macroscopic objects they compose, like chairs and tables. Other hierarchical theories assert that substances are more fundamental than their properties and that nature is more fundamental than culture. Flat ontologies, by contrast, deny that any entity has a privileged status, meaning that all entities exist on the same level. For them, the main question is only whether something exists rather than identifying
29930-576: The making of calendars . Professional astronomy is split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects. This data is then analyzed using basic principles of physics. Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. These two fields complement each other. Theoretical astronomy seeks to explain observational results and observations are used to confirm theoretical results. Astronomy
30135-469: The meaning of a statement is given by the procedure used to verify it, usually through the observations that would confirm it. Based on this controversial assumption, they argue that metaphysical statements are meaningless since they make no testable predictions about experience. A slightly weaker position allows metaphysical statements to have meaning while holding that metaphysical disagreements are merely verbal disputes about different ways to describe
30340-501: The method of eidetic variation is used to investigate essential structures underlying phenomena . This method involves imagining an object and varying its features to determine which ones are essential and cannot be changed. The transcendental method is a further approach and examines the metaphysical structure of reality by observing what entities there are and studying the conditions of possibility without which these entities could not exist. Some approaches give less importance to
30545-734: The mind used to order experience by classifying entities. Natural and social kinds are often understood as special types of universals. Entities belonging to the same natural kind share certain fundamental features characteristic of the structure of the natural world. In this regard, natural kinds are not an artificially constructed classification but are discovered, usually by the natural sciences, and include kinds like electrons , H 2 O , and tigers. Scientific realists and anti-realists disagree about whether natural kinds exist. Social kinds, like money and baseball , are studied by social metaphysics and characterized as useful social constructions that, while not purely fictional, do not reflect
30750-419: The more basic term by first characterizing things in terms of their essential features and then elaborating differences based on this conception. Differential ontologists, by contrast, privilege difference and say that the identity of a thing is a secondary determination that depends on how this thing differs from other things. Object-oriented ontology belongs to the school of speculative realism and examines
30955-672: The most basic level. Platonic realism asserts that universals have objective existence. Conceptualism says that universals only exist in the mind while nominalism denies their existence. There are similar disputes about mathematical objects , unobservable objects assumed by scientific theories, and moral facts . Materialism says that, fundamentally, there is only matter while dualism asserts that mind and matter are independent principles. According to some ontologists, there are no objective answers to ontological questions but only perspectives shaped by different linguistic practices. Ontology uses diverse methods of inquiry . They include
31160-593: The motions of objects visible to the naked eye. In some locations, early cultures assembled massive artifacts that may have had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops and in understanding the length of the year. As civilizations developed, most notably in Egypt , Mesopotamia , Greece , Persia , India , China , and Central America , astronomical observatories were assembled and ideas on
31365-417: The motions of the planets. Newton also developed the reflecting telescope . Improvements in the size and quality of the telescope led to further discoveries. The English astronomer John Flamsteed catalogued over 3000 stars. More extensive star catalogues were produced by Nicolas Louis de Lacaille . The astronomer William Herschel made a detailed catalog of nebulosity and clusters, and in 1781 discovered
31570-889: The natural sciences rely on concepts such as law of nature , causation, necessity, and spacetime to formulate their theories and predict or explain the outcomes of experiments. While scientists primarily focus on applying these concepts to specific situations, metaphysics examines their general nature and how they depend on each other. For instance, physicists formulate laws of nature, like laws of gravitation and thermodynamics , to describe how physical systems behave under various conditions. Metaphysicians, by contrast, examine what all laws of nature have in common, asking whether they merely describe contingent regularities or express necessary relations. New scientific discoveries have also influenced existing metaphysical theories and inspired new ones. Einstein's theory of relativity , for instance, prompted various metaphysicians to conceive space and time as
31775-405: The nature and role of objects. It sees objects as the fundamental building blocks of reality. As a flat ontology, it denies that some entities have a more fundamental form of existence than others. It uses this idea to argue that objects exist independently of human thought and perception. Methods of ontology are ways of conducting ontological inquiry and deciding between competing theories. There
31980-462: The nature of existence , the features all entities have in common, and their division into categories of being . An influential division is between particulars and universals . Particulars are individual unique entities, like a specific apple. Universals are general features that different particulars have in common, like the color red . Modal metaphysics examines what it means for something to be possible or necessary. Metaphysicians also explore
32185-406: The nature of the Universe began to develop. Most early astronomy consisted of mapping the positions of the stars and planets, a science now referred to as astrometry . From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon and the Earth in the Universe were explored philosophically. The Earth was believed to be the center of the Universe with
32390-401: The object is present, not the object as a whole. Change means that an earlier part is qualitatively different from a later part. For example, when a banana ripens, there is an unripe part followed by a ripe part. Causality is the relation between cause and effect whereby one entity produces or affects another entity. For instance, if a person bumps a glass and spills its contents then the bump
32595-471: The objective features of reality beyond sense experience, from critical metaphysics, which outlines the aspects and principles underlying all human thought and experience. Philosopher P. F. Strawson further explored the role of conceptual schemes, contrasting descriptive metaphysics, which articulates conceptual schemes commonly used to understand the world, with revisionary metaphysics, which aims to produce better conceptual schemes. Metaphysics differs from
32800-420: The objective or mind-independent reality of natural phenomena like elementary particles, lions, and stars. In the fields of computer science , information science , and knowledge representation , applied ontology is interested in the development of formal frameworks to encode and store information about a limited domain of entities in a structured way. A related application in genetics is Gene Ontology , which
33005-494: The observation of young stars embedded in molecular clouds and the cores of galaxies. Observations from the Wide-field Infrared Survey Explorer (WISE) have been particularly effective at unveiling numerous galactic protostars and their host star clusters . With the exception of infrared wavelengths close to visible light, such radiation is heavily absorbed by the atmosphere, or masked, as
33210-584: The ontological foundations of moral claims and religious doctrines. Beyond philosophy, its applications include the use of ontologies in artificial intelligence , economics , and sociology to classify entities. In psychiatry and medicine , it examines the metaphysical status of diseases . Meta-metaphysics is the metatheory of metaphysics and investigates the nature and methods of metaphysics. It examines how metaphysics differs from other philosophical and scientific disciplines and assesses its relevance to them. Even though discussions of these topics have
33415-480: The outcomes of experiments. Moral realists claim that there exist mind-independent moral facts. According to them, there are objective principles that determine which behavior is morally right. Moral anti-realists either claim that moral principles are subjective and differ between persons and cultures, a position known as moral relativism , or outright deny the existence of moral facts, a view referred to as moral nihilism . Monocategorical theories say that there
33620-553: The particles produced when cosmic rays hit the Earth's atmosphere. Gravitational-wave astronomy is an emerging field of astronomy that employs gravitational-wave detectors to collect observational data about distant massive objects. A few observatories have been constructed, such as the Laser Interferometer Gravitational Observatory LIGO . LIGO made its first detection on 14 September 2015, observing gravitational waves from
33825-465: The past. From the perspective of the B-series theory, time is static, and events are ordered by the temporal relations earlier-than and later-than without any essential difference between past, present, and future. Eternalism holds that past, present, and future are equally real, whereas presentism asserts that only entities in the present exist. Material objects persist through time and change in
34030-497: The planet Uranus , the first new planet found. During the 18–19th centuries, the study of the three-body problem by Leonhard Euler , Alexis Claude Clairaut , and Jean le Rond d'Alembert led to more accurate predictions about the motions of the Moon and planets. This work was further refined by Joseph-Louis Lagrange and Pierre Simon Laplace , allowing the masses of the planets and moons to be estimated from their perturbations. Significant advances in astronomy came about with
34235-470: The planets with great accuracy, a field known as celestial mechanics . More recently the tracking of near-Earth objects will allow for predictions of close encounters or potential collisions of the Earth with those objects. The measurement of stellar parallax of nearby stars provides a fundamental baseline in the cosmic distance ladder that is used to measure the scale of the Universe. Parallax measurements of nearby stars provide an absolute baseline for
34440-480: The possible consequences of these situations. For example, to explore the relation between matter and consciousness, some theorists compare humans to philosophical zombies —hypothetical creatures identical to humans but without conscious experience . A related method relies on commonly accepted beliefs instead of intuitions to formulate arguments and theories. The common-sense approach is often used to criticize metaphysical theories that deviate significantly from how
34645-596: The pre-colonial Middle Ages, but modern discoveries show otherwise. For over six centuries (from the recovery of ancient learning during the late Middle Ages into the Enlightenment), the Roman Catholic Church gave more financial and social support to the study of astronomy than probably all other institutions. Among the Church's motives was finding the date for Easter . Medieval Europe housed
34850-508: The process, like a tree that grows or loses leaves. The main ways of conceptualizing persistence through time are endurantism and perdurantism . According to endurantism, material objects are three-dimensional entities that are wholly present at each moment. As they change, they gain or lose properties but otherwise remain the same. Perdurantists see material objects as four-dimensional entities that extend through time and are made up of different temporal parts . At each moment, only one part of
35055-458: The properties examined include luminosity , density , temperature , and chemical composition. Because astrophysics is a very broad subject, astrophysicists typically apply many disciplines of physics, including mechanics , electromagnetism , statistical mechanics , thermodynamics , quantum mechanics , relativity , nuclear and particle physics , and atomic and molecular physics . In practice, modern astronomical research often involves
35260-473: The properties of more distant stars, as their properties can be compared. Measurements of the radial velocity and proper motion of stars allow astronomers to plot the movement of these systems through the Milky Way galaxy. Astrometric results are the basis used to calculate the distribution of speculated dark matter in the galaxy. During the 1990s, the measurement of the stellar wobble of nearby stars
35465-403: The property red . States of affairs are complex particular entities that have several other entities as their components. The state of affairs "Socrates is wise" has two components: the individual Socrates and the property wise . States of affairs that correspond to reality are called facts . Facts are truthmakers of statements, meaning that whether a statement is true or false depends on
35670-459: The question of whether extraterrestrial life exists, and how humans can detect it if it does. The term exobiology is similar. Astrobiology makes use of molecular biology , biophysics , biochemistry , chemistry , astronomy, physical cosmology , exoplanetology and geology to investigate the possibility of life on other worlds and help recognize biospheres that might be different from that on Earth. The origin and early evolution of life
35875-671: The questions about the relation between body and mind, whether the nature of the human mind is historically fixed, and what the metaphysical status of diseases is. Metaphysics is similar to both physical cosmology and theology in its exploration of the first causes and the universe as a whole. Key differences are that metaphysics relies on rational inquiry while physical cosmology gives more weight to empirical observations and theology incorporates divine revelation and other faith-based doctrines. Historically, cosmology and theology were considered subfields of metaphysics. Astronomy Astronomy
36080-464: The realm beyond sensory experience. A related argument favoring the unreliability of metaphysical theorizing points to the deep and lasting disagreements about metaphysical issues, suggesting a lack of overall progress. Another criticism holds that the problem lies not with human cognitive abilities but with metaphysical statements themselves, which some claim are neither true nor false but meaningless . According to logical positivists , for instance,
36285-448: The realm of physics and its focus on empirical observation. Metaphysics may have received its name by a historical accident when Aristotle's book on this subject was published. Aristotle did not use the term metaphysics but his editor (likely Andronicus of Rhodes ) may have coined it for its title to indicate that this book should be studied after Aristotle's book published on physics : literally ' after physics ' . The term entered
36490-433: The relation between free will and causal determinism —the view that everything in the universe, including human behavior, is determined by preceding events and laws of nature. It is controversial whether causal determinism is true, and, if so, whether this would imply that there is no free will. According to incompatibilism , free will cannot exist in a deterministic world since there is no true choice or control if everything
36695-425: The rotation of the Earth, furthermore, Buridan also developed the theory of impetus (predecessor of the modern scientific theory of inertia ) which was able to show planets were capable of motion without the intervention of angels. Georg von Peuerbach (1423–1461) and Regiomontanus (1436–1476) helped make astronomical progress instrumental to Copernicus's development of the heliocentric model decades later. During
36900-425: The same features, such as perfect identical twins. This is also called exact similarity and indiscernibility . Numerical identity, by contrast, means that there is only a single entity. For example, if Fatima is the mother of Leila and Hugo then Leila's mother is numerically identical to Hugo's mother. Another distinction is between synchronic and diachronic identity. Synchronic identity relates an entity to itself at
37105-431: The same time, whereas diachronic identity is about the same entity at different times, as in statements like "the table I bought last year is the same as the table in my dining room now". Personal identity is a related topic in metaphysics that uses the term identity in a slightly different sense and concerns questions like what personhood is or what makes someone a person. Various contemporary metaphysicians rely on
37310-440: The same time. Diachronic identity relates an entity to itself at different times, as in "the woman who bore Leila three years ago is the same woman who bore Hugo this year". There are different and sometimes overlapping ways to divide ontology into branches. Pure ontology focuses on the most abstract topics associated with the concept and nature of being. It is not restricted to a specific domain of entities and studies existence and
37515-559: The same time. For example, the particulars Nelson Mandela and Mahatma Gandhi instantiate the universal humanity , similar to how a strawberry and a ruby instantiate the universal red . A topic discussed since ancient philosophy, the problem of universals consists in the challenge of characterizing the ontological status of universals. Realists argue that universals are real, mind-independent entities that exist in addition to particulars. According to Platonic realists , universals exist independently of particulars, which implies that
37720-418: The science of the first causes and as the study of being qua being, that is, the topic of what all beings have in common and to what fundamental categories they belong. In the modern period, the scope of metaphysics expanded to include topics such as the distinction between mind and body and free will . Some philosophers follow Aristotle in describing metaphysics as "first philosophy", suggesting that it
37925-404: The second entity. For instance, the surface of an apple cannot exist without the apple. An entity is ontologically independent if it does not depend on anything else, meaning that it is fundamental and can exist on its own. Ontological dependence plays a central role in ontology and its attempt to describe reality on its most fundamental level. It is closely related to metaphysical grounding , which
38130-517: The sentence "some electrons are bonded to protons" is true then it can be used to justify that electrons and protons exist. Quine used this insight to argue that one can learn about metaphysics by closely analyzing scientific claims to understand what kind of metaphysical picture of the world they presuppose. In addition to methods of conducting metaphysical inquiry, there are various methodological principles used to decide between competing theories by comparing their theoretical virtues. Ockham's Razor
38335-436: The stars" depending on the translation). Astronomy should not be confused with astrology , the belief system which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin, they are now entirely distinct. "Astronomy" and " astrophysics " are synonyms. Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside
38540-417: The structure of reality as a whole. Pure ontology contrasts with applied ontology , also called domain ontology. Applied ontology examines the application of ontological theories and principles to specific disciplines and domains, often in the field of science. It considers ontological problems in regard to specific entities such as matter , mind , numbers , God , and cultural artifacts. Social ontology ,
38745-477: The subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject. However, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Some fields, such as astrometry , are purely astronomy rather than also astrophysics. Various departments in which scientists carry out research on this subject may use "astronomy" and "astrophysics", partly depending on whether
38950-517: The temporal relation of coming before . In the metaphysics of time, an important contrast is between the A-series and the B-series . According to the A-series theory, the flow of time is real, meaning that events are categorized into the past, present, and future. The present continually moves forward in time and events that are in the present now will eventually change their status and lie in
39155-478: The underlying facts. Events are particular entities that occur in time, like the fall of the Berlin Wall and the first moon landing . They usually involve some kind of change, like the lawn becoming dry. In some cases, no change occurs, like the lawn staying wet. Complex events, also called processes , are composed of a sequence of events. Concrete objects are entities that exist in space and time, such as
39360-408: The underlying faculties responsible for these phenomena. The mind–body problem is the challenge of clarifying the relation between physical and mental phenomena. According to Cartesian dualism , minds and bodies are distinct substances. They causally interact with each other in various ways but can, at least in principle, exist on their own. This view is rejected by monists , who argue that reality
39565-475: The universal red would continue to exist even if there were no red things. A more moderate form of realism , inspired by Aristotle, states that universals depend on particulars, meaning that they are only real if they are instantiated. Nominalists reject the idea that universals exist in either form. For them, the world is composed exclusively of particulars. Conceptualists offer an intermediate position, stating that universals exist, but only as concepts in
39770-548: The universe consists of a multitude of galaxies. With this Hubble formulated the Hubble constant , which allowed for the first time a calculation of the age of the Universe and size of the Observable Universe, which became increasingly precise with better meassurements, starting at 2 billion years and 280 million light-years, until 2006 when data of the Hubble Space Telescope allowed a very accurate calculation of
39975-409: The universe; origin of cosmic rays ; general relativity and physical cosmology , including string cosmology and astroparticle physics . Astrochemistry is the study of the abundance and reactions of molecules in the Universe , and their interaction with radiation . The discipline is an overlap of astronomy and chemistry . The word "astrochemistry" may be applied to both the Solar System and
40180-553: The word ontology traces back to the ancient Greek terms ὄντως ( ontos , meaning ' being ' ) and λογία ( logia , meaning ' study of ' ), literally, ' the study of being ' . The ancient Greeks did not use the term ontology , which was coined by philosophers in the 17th century. Being, or existence , is the main topic of ontology. It is one of the most general and fundamental concepts, encompassing all of reality and every entity within it. In its broadest sense, being only contrasts with non-being or nothingness. It
40385-806: The world is entirely composed of particular objects. Mathematical realism , a closely related view in the philosophy of mathematics , says that mathematical facts exist independently of human language, thought, and practices and are discovered rather than invented. According to mathematical Platonism, this is the case because of the existence of mathematical objects , like numbers and sets. Mathematical Platonists say that mathematical objects are as real as physical objects, like atoms and stars, even though they are not accessible to empirical observation . Influential forms of mathematical anti-realism include conventionalism, which says that mathematical theories are trivially true simply by how mathematical terms are defined, and game formalism , which understands mathematics not as
40590-419: The world. According to this view, the disagreement in the metaphysics of composition about whether there are tables or only particles arranged table-wise is a trivial debate about linguistic preferences without any substantive consequences for the nature of reality. The position that metaphysical disputes have no meaning or no significant point is called metaphysical or ontological deflationism . This view
40795-452: The world. Aristotelian realism, also called moderate realism , rejects this idea and says that universals only exist as long as there are objects that exemplify them. Conceptualism , by contrast, is a form of anti-realism, stating that universals only exist in the mind as concepts that people use to understand and categorize the world. Nominalists defend a strong form of anti-realism by saying that universals have no existence. This means that
41000-437: The world. Facts, also known as states of affairs, are complex entities; for example, the fact that the Earth is a planet consists of the particular object the Earth and the property being a planet . Fact ontologies state that facts are the fundamental constituents of reality, meaning that objects, properties, and relations cannot exist on their own and only form part of reality to the extent that they participate in facts. In
41205-640: Was used to detect large extrasolar planets orbiting those stars. Theoretical astronomers use several tools including analytical models and computational numerical simulations ; each has its particular advantages. Analytical models of a process are better for giving broader insight into the heart of what is going on. Numerical models reveal the existence of phenomena and effects otherwise unobserved. Theorists in astronomy endeavor to create theoretical models that are based on existing observations and known physics, and to predict observational consequences of those models. The observation of phenomena predicted by
41410-520: Was an early analog computer designed to calculate the location of the Sun , Moon , and planets for a given date. Technological artifacts of similar complexity did not reappear until the 14th century, when mechanical astronomical clocks appeared in Europe. Astronomy flourished in the Islamic world and other parts of the world. This led to the emergence of the first astronomical observatories in
41615-419: Was born at a different date. Using this idea, possible world semantics says that a sentence is possibly true if it is true in at least one possible world. A sentence is necessarily true if it is true in all possible worlds. In ontology, identity means that two things are the same. Philosophers distinguish between qualitative and numerical identity. Two entities are qualitatively identical if they have exactly
41820-536: Was formulated, heavily evidenced by cosmic microwave background radiation , Hubble's law , and the cosmological abundances of elements . Space telescopes have enabled measurements in parts of the electromagnetic spectrum normally blocked or blurred by the atmosphere. In February 2016, it was revealed that the LIGO project had detected evidence of gravitational waves in the previous September. The main source of information about celestial bodies and other objects
42025-452: Was proposed by Aristotle, who outlined a system of 10 categories . He argued that substances (e.g. man and horse), are the most important category since all other categories like quantity (e.g. four), quality (e.g. white), and place (e.g. in Athens) are said of substances and depend on them. Kant understood categories as fundamental principles underlying human understanding and developed
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