124-464: In metaphysics , impenetrability is the name given to that quality of matter whereby two bodies cannot occupy the same space at the same time. The philosopher John Toland argued that impenetrability and extension were sufficient to define matter, a contention strongly disputed by Gottfried Wilhelm von Leibniz . Locke considered impenetrability to be "more a consequence of solidity , than solidity itself." This article about metaphysics
248-529: A causal relation . General relativity does not address the nature of time for extremely small intervals where quantum mechanics holds. In quantum mechanics, time is treated as a universal and absolute parameter, differing from general relativity's notion of independent clocks. The problem of time consists of reconciling these two theories. As of 2024, there is no generally accepted theory of quantum general relativity. Generally speaking, methods of temporal measurement, or chronometry , take two distinct forms:
372-745: 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,
496-617: A calendar based solely on twelve lunar months. Lunisolar calendars have a thirteenth month added to some years to make up for the difference between a full year (now known to be about 365.24 days) and a year of just twelve lunar months. The numbers twelve and thirteen came to feature prominently in many cultures, at least partly due to this relationship of months to years. Other early forms of calendars originated in Mesoamerica, particularly in ancient Mayan civilization. These calendars were religiously and astronomically based, with 18 months in
620-620: A dimension. Isaac Newton said that we are merely occupying time, he also says that humans can only understand relative time . Relative time is a measurement of objects in motion. The anti-realists believed that time is merely a convenient intellectual concept for humans to understand events. This means that time was useless unless there were objects that it could interact with, this was called relational time . René Descartes , John Locke , and David Hume said that one's mind needs to acknowledge time, in order to understand what time is. Immanuel Kant believed that we can not know what something
744-400: 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
868-414: 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
992-403: A head in the famous Leibniz–Clarke correspondence . Philosophers in the 17th and 18th century questioned if time was real and absolute, or if it was an intellectual concept that humans use to understand and sequence events. These questions lead to realism vs anti-realism; the realists believed that time is a fundamental part of the universe, and be perceived by events happening in a sequence, in
1116-422: 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
1240-407: A hundred minutes of a hundred seconds, which marked a deviation from the base 12 ( duodecimal ) system used in many other devices by many cultures. The system was abolished in 1806. A large variety of devices have been invented to measure time. The study of these devices is called horology . An Egyptian device that dates to c. 1500 BC , similar in shape to a bent T-square , measured
1364-568: 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
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#17327829938781488-475: 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
1612-577: A number or calendar date to an instant (point in time), quantifying the duration of a time interval, and establishing a chronology (ordering of events). In modern times, several time specifications have been officially recognized as standards, where formerly they were matters of custom and practice. The invention in 1955 of the caesium atomic clock has led to the replacement of older and purely astronomical time standards such as sidereal time and ephemeris time , for most practical purposes, by newer time standards based wholly or partly on atomic time using
1736-488: A prime motivation in navigation and astronomy . Time is also of significant social importance, having economic value (" time is money ") as well as personal value, due to an awareness of the limited time in each day and in human life spans . The concept of time can be complex. Multiple notions exist and defining time in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports,
1860-479: 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
1984-475: 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
2108-486: A recurring pattern of ages or cycles, where events and phenomena repeated themselves in a predictable manner. One of the most famous examples of this concept is found in Hindu philosophy , where time is depicted as a wheel called the " Kalachakra " or "Wheel of Time." According to this belief, the universe undergoes endless cycles of creation, preservation, and destruction. Similarly, in other ancient cultures such as those of
2232-465: 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
2356-402: 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
2480-464: 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
2604-461: 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,
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#17327829938782728-401: 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
2852-621: 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
2976-525: A year and 20 days in a month, plus five epagomenal days at the end of the year. The reforms of Julius Caesar in 45 BC put the Roman world on a solar calendar . This Julian calendar was faulty in that its intercalation still allowed the astronomical solstices and equinoxes to advance against it by about 11 minutes per year. Pope Gregory XIII introduced a correction in 1582; the Gregorian calendar
3100-452: Is a stub . You can help Misplaced Pages by expanding it . Metaphysics Metaphysics is the branch of philosophy that examines the basic structure of reality . It 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
3224-399: 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
3348-435: 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
3472-768: Is a fundamental concept to define other quantities, such as velocity . To avoid a circular definition, time in physics is operationally defined as "what a clock reads", specifically a count of repeating events such as the SI second . Although this aids in practical measurements, it does not address the essence of time. Physicists developed the concept of the spacetime continuum, where events are assigned four coordinates: three for space and one for time. Events like particle collisions , supernovas , or rocket launches have coordinates that may vary for different observers, making concepts like "now" and "here" relative. In general relativity , these coordinates do not directly correspond to
3596-521: 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
3720-458: Is a theoretical ideal scale realized by TAI. Geocentric Coordinate Time and Barycentric Coordinate Time are scales defined as coordinate times in the context of the general theory of relativity. Barycentric Dynamical Time is an older relativistic scale that is still in use. Many ancient cultures, particularly in the East, had a cyclical view of time. In these traditions, time was often seen as
3844-442: 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
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3968-440: 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
4092-430: Is credited to Egyptians because of their sundials, which operated on a duodecimal system. The importance of the number 12 is due to the number of lunar cycles in a year and the number of stars used to count the passage of night. The most precise timekeeping device of the ancient world was the water clock , or clepsydra , one of which was found in the tomb of Egyptian pharaoh Amenhotep I . They could be used to measure
4216-401: 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
4340-400: 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
4464-500: Is dominated by temporality ( kala ), everything within time is subject to change and decay. Overcoming pain and death requires knowledge that transcends temporal existence and reveals its eternal foundation. Two contrasting viewpoints on time divide prominent philosophers. One view is that time is part of the fundamental structure of the universe – a dimension independent of events, in which events occur in sequence . Isaac Newton subscribed to this realist view, and hence it
4588-436: 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
4712-420: 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
4836-504: Is in Byrhtferth 's Enchiridion (a science text) of 1010–1012, where it was defined as 1/564 of a momentum (1 1 ⁄ 2 minutes), and thus equal to 15/94 of a second. It was used in the computus , the process of calculating the date of Easter. As of May 2010 , the smallest time interval uncertainty in direct measurements is on the order of 12 attoseconds (1.2 × 10 seconds), about 3.7 × 10 Planck times . The second (s)
4960-434: 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,
5084-816: Is kept within 0.9 second of UT1 by the introduction of one-second steps to UTC, the leap second . The Global Positioning System broadcasts a very precise time signal based on UTC time. The surface of the Earth is split into a number of time zones . Standard time or civil time in a time zone deviates a fixed, round amount, usually a whole number of hours, from some form of Universal Time, usually UTC. Most time zones are exactly one hour apart, and by convention compute their local time as an offset from UTC. For example, time zones at sea are based on UTC. In many locations (but not at sea) these offsets vary twice yearly due to daylight saving time transitions. Some other time standards are used mainly for scientific work. Terrestrial Time
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5208-468: 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
5332-479: Is more fundamental than other forms of philosophical inquiry. Metaphysics encompasses a wide range of general and abstract topics. It investigates 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
5456-411: Is neither an event nor a thing, and thus is not itself measurable nor can it be travelled. Furthermore, it may be that there is a subjective component to time, but whether or not time itself is "felt", as a sensation, or is a judgment, is a matter of debate. In Philosophy, time was questioned throughout the centuries; what time is and if it is real or not. Ancient Greek philosophers asked if time
5580-419: 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,
5704-483: Is not rather than what it is, an approach similar to that taken in other negative definitions . However, Augustine ends up calling time a "distention" of the mind (Confessions 11.26) by which we simultaneously grasp the past in memory, the present by attention, and the future by expectation. Isaac Newton believed in absolute space and absolute time; Leibniz believed that time and space are relational. The differences between Leibniz's and Newton's interpretations came to
5828-411: 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
5952-408: 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
6076-457: 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
6200-666: Is qualitative, as opposed to quantitative. In Greek mythology, Chronos (ancient Greek: Χρόνος) is identified as the Personification of Time. His name in Greek means "time" and is alternatively spelled Chronus (Latin spelling) or Khronos. Chronos is usually portrayed as an old, wise man with a long, gray beard, such as "Father Time". Some English words whose etymological root is khronos/chronos include chronology , chronometer , chronic , anachronism , synchronise , and chronicle . Rabbis sometimes saw time like "an accordion that
6324-448: 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
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#17327829938786448-600: Is seen as progressing in a straight line from past to future without repetition. In general, the Islamic and Judeo-Christian world-view regards time as linear and directional , beginning with the act of creation by God. The traditional Christian view sees time ending, teleologically, with the eschatological end of the present order of things, the " end time ". In the Old Testament book Ecclesiastes , traditionally ascribed to Solomon (970–928 BC), time (as
6572-447: Is sometimes referred to as Newtonian time . The opposing view is that time does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure (together with space and number) within which humans sequence and compare events. This second view, in the tradition of Gottfried Leibniz and Immanuel Kant , holds that time
6696-418: 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
6820-402: Is the SI base unit. A minute (min) is 60 seconds in length (or, rarely, 59 or 61 seconds when leap seconds are employed), and an hour is 60 minutes or 3600 seconds in length. A day is usually 24 hours or 86,400 seconds in length; however, the duration of a calendar day can vary due to Daylight saving time and Leap seconds . A time standard is a specification for measuring time: assigning
6944-406: 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
7068-401: Is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past , through the present , and into the future . It is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in
7192-417: 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
7316-433: Is the primary framework for understanding how spacetime works. Through advances in both theoretical and experimental investigations of spacetime, it has been shown that time can be distorted and dilated , particularly at the edges of black holes . Throughout history, time has been an important subject of study in religion, philosophy, and science. Temporal measurement has occupied scientists and technologists and has been
7440-401: 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
7564-465: 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
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#17327829938787688-578: The Clock of the Long Now . They can be driven by a variety of means, including gravity, springs, and various forms of electrical power, and regulated by a variety of means such as a pendulum . Alarm clocks first appeared in ancient Greece around 250 BC with a water clock that would set off a whistle. This idea was later mechanized by Levi Hutchins and Seth E. Thomas . A chronometer is a portable timekeeper that meets certain precision standards. Initially,
7812-510: 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
7936-425: The calendar , a mathematical tool for organising intervals of time, and the clock , a physical mechanism that counts the passage of time. In day-to-day life, the clock is consulted for periods less than a day, whereas the calendar is consulted for periods longer than a day. Increasingly, personal electronic devices display both calendars and clocks simultaneously. The number (as on a clock dial or calendar) that marks
8060-502: The conscious experience . Time is often referred to as a fourth dimension , along with three spatial dimensions . Time is one of the seven fundamental physical quantities in both the International System of Units (SI) and International System of Quantities . The SI base unit of time is the second , which is defined by measuring the electronic transition frequency of caesium atoms. General relativity
8184-404: 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
8308-627: 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
8432-523: 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
8556-622: The Hebrew word עידן, זמן iddan (age, as in "Ice age") zĕman(time) is often translated) is a medium for the passage of predestined events. (Another word, زمان" זמן" zamān , meant time fit for an event , and is used as the modern Arabic , Persian , and Hebrew equivalent to the English word "time".) The Greek language denotes two distinct principles, Chronos and Kairos . The former refers to numeric, or chronological, time. The latter, literally "the right or opportune moment", relates specifically to metaphysical or Divine time. In theology, Kairos
8680-529: The Mayans, Aztecs, and Chinese, there were also beliefs in cyclical time, often associated with astronomical observations and calendars. These cultures developed complex systems to track time, seasons, and celestial movements, reflecting their understanding of cyclical patterns in nature and the universe. The cyclical view of time contrasts with the linear concept of time more common in Western thought, where time
8804-480: The Middle Dutch word klocke which, in turn, derives from the medieval Latin word clocca , which ultimately derives from Celtic and is cognate with French, Latin, and German words that mean bell . The passage of the hours at sea was marked by bells and denoted the time (see ship's bell ). The hours were marked by bells in abbeys as well as at sea. Clocks can range from watches to more exotic varieties such as
8928-517: The SI second. International Atomic Time (TAI) is the primary international time standard from which other time standards are calculated. Universal Time (UT1) is mean solar time at 0° longitude, computed from astronomical observations. It varies from TAI because of the irregularities in Earth's rotation. Coordinated Universal Time (UTC) is an atomic time scale designed to approximate Universal Time. UTC differs from TAI by an integral number of seconds. UTC
9052-402: 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
9176-430: 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 ,
9300-523: The causal structure of events. Instead, the spacetime interval is calculated and classified as either space-like or time-like, depending on whether an observer exists that would say the events are separated by space or by time. Since the time required for light to travel a specific distance is the same for all observers—a fact first publicly demonstrated by the Michelson–Morley experiment —all observers will consistently agree on this definition of time as
9424-625: The color red . Modal metaphysics examines what it means for something to be possible or necessary. Metaphysicians also explore 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
9548-404: 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
9672-768: 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
9796-452: 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
9920-496: 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
10044-523: The events of the abbeys and monasteries of the Middle Ages. Richard of Wallingford (1292–1336), abbot of St. Alban's abbey, famously built a mechanical clock as an astronomical orrery about 1330. Great advances in accurate time-keeping were made by Galileo Galilei and especially Christiaan Huygens with the invention of pendulum-driven clocks along with the invention of the minute hand by Jost Burgi. The English word clock probably comes from
10168-744: 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
10292-447: 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
10416-439: The first mechanical clocks driven by an escapement mechanism. The hourglass uses the flow of sand to measure the flow of time. They were used in navigation. Ferdinand Magellan used 18 glasses on each ship for his circumnavigation of the globe (1522). Incense sticks and candles were, and are, commonly used to measure time in temples and churches across the globe. Water clocks, and, later, mechanical clocks, were used to mark
10540-481: The frequency of electronic transitions in certain atoms to measure the second. One of the atoms used is caesium ; most modern atomic clocks probe caesium with microwaves to determine the frequency of these electron vibrations. Since 1967, the International System of Measurements bases its unit of time, the second, on the properties of caesium atoms. SI defines the second as 9,192,631,770 cycles of
10664-468: 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
10788-438: The hours even at night but required manual upkeep to replenish the flow of water. The ancient Greeks and the people from Chaldea (southeastern Mesopotamia) regularly maintained timekeeping records as an essential part of their astronomical observations. Arab inventors and engineers, in particular, made improvements on the use of water clocks up to the Middle Ages. In the 11th century, Chinese inventors and engineers invented
10912-404: 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
11036-443: 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
11160-415: 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
11284-469: 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
11408-501: 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
11532-734: 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
11656-889: 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
11780-583: The nature of time. Plato , in the Timaeus , identified time with the period of motion of the heavenly bodies. Aristotle , in Book IV of his Physica defined time as 'number of movement in respect of the before and after'. In Book 11 of his Confessions , St. Augustine of Hippo ruminates on the nature of time, asking, "What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not." He begins to define time by what it
11904-401: 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
12028-471: 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
12152-511: The occurrence of a specified event as to hour or date is obtained by counting from a fiducial epoch – a central reference point. Artifacts from the Paleolithic suggest that the moon was used to reckon time as early as 6,000 years ago. Lunar calendars were among the first to appear, with years of either 12 or 13 lunar months (either 354 or 384 days). Without intercalation to add days or months to some years, seasons quickly drift in
12276-584: 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
12400-419: The passage of time from the shadow cast by its crossbar on a nonlinear rule. The T was oriented eastward in the mornings. At noon, the device was turned around so that it could cast its shadow in the evening direction. A sundial uses a gnomon to cast a shadow on a set of markings calibrated to the hour. The position of the shadow marks the hour in local time . The idea to separate the day into smaller parts
12524-465: 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
12648-480: 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
12772-508: 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
12896-661: 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. Time Time
13020-641: The radiation that corresponds to the transition between two electron spin energy levels of the ground state of the Cs atom. Today, the Global Positioning System in coordination with the Network Time Protocol can be used to synchronize timekeeping systems across the globe. In medieval philosophical writings, the atom was a unit of time referred to as the smallest possible division of time. The earliest known occurrence in English
13144-464: 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,
13268-448: 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
13392-433: 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
13516-431: 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
13640-559: 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
13764-418: 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
13888-576: The sciences, and the performing arts all incorporate some notion of time into their respective measuring systems . Traditional definitions of time involved the observation of periodic motion such as the apparent motion of the sun across the sky, the phases of the moon, and the passage of a free-swinging pendulum. More modern systems include the Global Positioning System , other satellite systems, Coordinated Universal Time and mean solar time . Although these systems differ from one another, with careful measurements they can be synchronized. In physics, time
14012-517: 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
14136-517: 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
14260-584: The term was used to refer to the marine chronometer , a timepiece used to determine longitude by means of celestial navigation , a precision first achieved by John Harrison . More recently, the term has also been applied to the chronometer watch , a watch that meets precision standards set by the Swiss agency COSC . The most accurate timekeeping devices are atomic clocks , which are accurate to seconds in many millions of years, and are used to calibrate other clocks and timekeeping instruments. Atomic clocks use
14384-408: 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
14508-475: 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
14632-419: 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
14756-485: Was an illusion to humans. Plato believed that time was made by the Creator at the same instant as the heavens. He also says that time is a period of motion of the heavenly bodies . Aristotle believed that time correlated to movement, that time did not exist on its own but was relative to motion of objects. He also believed that time was related to the motion of celestial bodies ; the reason that humans can tell time
14880-466: Was because of orbital periods and therefore there was a duration on time. The Vedas , the earliest texts on Indian philosophy and Hindu philosophy dating to the late 2nd millennium BC , describe ancient Hindu cosmology , in which the universe goes through repeated cycles of creation, destruction and rebirth, with each cycle lasting 4,320 million years. Ancient Greek philosophers , including Parmenides and Heraclitus , wrote essays on
15004-480: Was expanded and collapsed at will." According to Kabbalists , "time" is a paradox and an illusion . According to Advaita Vedanta , time is integral to the phenomenal world, which lacks independent reality. Time and the phenomenal world are products of maya , influenced by our senses, concepts, and imaginations. The phenomenal world, including time, is seen as impermanent and characterized by plurality, suffering, conflict, and division. Since phenomenal existence
15128-466: Was linear or cyclical and if time was endless or finite . These philosophers had different ways of explaining time; for instance, ancient Indian philosophers had something called the Wheel of Time. It is believed that there was repeating ages over the lifespan of the universe. This led to beliefs like cycles of rebirth and reincarnation . The Greek philosophers believe that the universe was infinite, and
15252-533: Was only slowly adopted by different nations over a period of centuries, but it is now by far the most commonly used calendar around the world. During the French Revolution , a new clock and calendar were invented as part of the dechristianization of France and to create a more rational system in order to replace the Gregorian calendar. The French Republican Calendar 's days consisted of ten hours of
15376-452: 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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