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This article is about the natural philosophy regarding the fundamental composition of the physical world. For other uses, see Atomism (disambiguation). Atomism (from Greek ἄτομον, atomon, i.e. "uncuttable, indivisible")[1][2][3] is a natural philosophy proposing that the physical universe is composed of fundamental indivisible components known as atoms. References to the concept of atomism and its atoms appeared in both ancient Greek and ancient Indian philosophical traditions. Leucippus is the earliest figure whose commitment to atomism is well attested and he is usually credited with inventing atomism.[4] He and other ancient Greek atomists theorized that nature consists of two fundamental principles: atom and void. Clusters of different shapes, arrangements, and positions give rise to the various macroscopic substances in the world.[5][4] The particles of chemical matter for which chemists and other natural philosophers of the early 19th century found experimental evidence were thought to be indivisible, and therefore were given by John Dalton the name "atom", long used by the atomist philosophy. Although the connection to historical atomism is at best tenuous, elementary particles have become a modern analogue of philosophical atoms. Contents 1Reductionism 2History 2.1Antiquity 2.1.1Greek atomism 2.1.1.1Democritus 2.1.1.2Geometry and atoms 2.1.1.3Rejection in Aristotelianism 2.1.1.4Later ancient atomism 2.1.1.5Atomism and ethics 2.1.2Indian atomism 2.2Middle Ages 2.2.1Medieval Hinduism 2.2.2Medieval Buddhism 2.2.3Medieval Islam 2.2.4Medieval Christendom 2.3Atomist renaissance 2.3.1Corpuscularianism 2.4Modern atomic theory 3See also 4Notes 5References 6External links Reductionism[edit] Philosophical atomism is a reductive argument, proposing not only that everything is composed of atoms and void, but that nothing they compose really exists: the only things that really exist are atoms ricocheting off each other mechanistically in an otherwise empty void. Atomism stands in contrast to a substance theory wherein a prime material continuum remains qualitatively invariant under division (for example, the ratio of the four classical elements would be the same in any portion of a homogeneous material). Indian Buddhists, such as Dharmakirti (fl. c. 6th or 7th century) and others, developed distinctive theories of atomism, for example, involving momentary (instantaneous) atoms (kalapas) that flash in and out of existence. History[edit] Antiquity[edit] Greek atomism[edit] Democritus[edit] In the 5th century BC, Leucippus and his pupil Democritus proposed that all matter was composed of small indivisible particles which they called "atoms".[6][7][8][9] Nothing whatsoever is known about Leucippus except that he was the teacher of Democritus.[9] Democritus, by contrast, wrote prolifically, producing over eighty known treatises, none of which have survived to the present day complete.[9] However, a massive number of fragments and quotations of his writings have survived.[9] These are the main source of information on his teachings about atoms.[9] Democritus's argument for the existence of atoms hinged on the idea that it is impossible to keep dividing matter infinitely - and that matter must therefore be made up of extremely tiny particles.[9] The atomistic theory aimed to remove the "distinction which the Eleatic school drew between the Absolute, or the only real existence, and the world of change around us."[10] Democritus believed that atoms are too small for human senses to detect, that they are infinitely many, that they come in infinitely many varieties, and that they have always existed.[9] They float in a vacuum, which Democritus called the "void",[9] and they vary in form, order, and posture.[9] Some atoms, he maintained, are convex, others concave, some shaped like hooks, and others like eyes.[9] They are constantly moving and colliding into each other.[9] Democritus wrote that atoms and void are the only things that exist and that all other things are merely said to exist by social convention.[9] The objects humans see in everyday life are composed of many atoms united by random collisions and their forms and materials are determined by what kinds of atom make them up.[9] Likewise, human perceptions are caused by atoms as well.[9] Bitterness is caused by small, angular, jagged atoms passing across the tongue;[9] whereas sweetness is caused by larger, smoother, more rounded atoms passing across the tongue.[9] Previously, Parmenides had denied the existence of motion, change and void. He believed all existence to be a single, all-encompassing and unchanging mass (a concept known as monism), and that change and motion were mere illusions. He explicitly rejected sensory experience as the path to an understanding of the universe and instead used purely abstract reasoning. He believed there is no such thing as void, equating it with non-being. This in turn meant that motion is impossible, because there is no void to move into.[11] Parmenides doesn't mention or explicitly deny the existence of the void, stating instead that what is not does not exist.[12][13][14] He also wrote all that is must be an indivisible unity, for if it were manifold, then there would have to be a void that could divide it. Finally, he stated that the all encompassing Unity is unchanging, for the Unity already encompasses all that is and can be.[11] Democritus accepted most of Parmenides' arguments, except for the idea that change is an illusion. He believed change was real, and if it was not then at least the illusion had to be explained. He thus supported the concept of void, and stated that the universe is made up of many Parmenidean entities that move around in the void.[11] The void is infinite and provides the space in which the atoms can pack or scatter differently. The different possible packings and scatterings within the void make up the shifting outlines and bulk of the objects that organisms feel, see, eat, hear, smell, and taste. While organisms may feel hot or cold, hot and cold actually have no real existence. They are simply sensations produced in organisms by the different packings and scatterings of the atoms in the void that compose the object that organisms sense as being "hot" or "cold". The work of Democritus survives only in secondhand reports, some of which are unreliable or conflicting. Much of the best evidence of Democritus' theory of atomism is reported by Aristotle (384–322 BCE) in his discussions of Democritus' and Plato's contrasting views on the types of indivisibles composing the natural world.[15] Geometry and atoms[edit] This section possibly contains original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (June 2021) (Learn how and when to remove this template message) Element Polyhedron Number of Faces Number of Triangles Fire Tetrahedron (Animation) 4 24 Air Octahedron (Animation) 8 48 Water Icosahedron (Animation) 20 120 Earth Cube (Animation) 6 24 Geometrical simple bodies according to Plato Plato (c. 427 – c. 347 BCE), if he had been familiar with the atomism of Democritus, would have objected to its mechanistic materialism. He argued that atoms just crashing into other atoms could never produce the beauty and form of the world. In Plato's Timaeus (28b–29a) the character of Timeaus insisted that the cosmos was not eternal but was created, although its creator framed it after an eternal, unchanging model.[16] One part of that creation were the four simple bodies of fire, air, water, and earth. But Plato did not consider these corpuscles to be the most basic level of reality, for in his view they were made up of an unchanging level of reality, which was mathematical. These simple bodies were geometric solids, the faces of which were, in turn, made up of triangles. The square faces of the cube were each made up of four isosceles right-angled triangles and the triangular faces of the tetrahedron, octahedron, and icosahedron were each made up of six right-angled triangles. Plato postulated the geometric structure of the simple bodies of the four elements as summarized in the adjacent table. The cube, with its flat base and stability, was assigned to earth; the tetrahedron was assigned to fire because its penetrating points and sharp edges made it mobile. The points and edges of the octahedron and icosahedron were blunter and so these less mobile bodies were assigned to air and water. Since the simple bodies could be decomposed into triangles, and the triangles reassembled into atoms of different elements, Plato's model offered a plausible account of changes among the primary substances.[17][18] Rejection in Aristotelianism[edit] Sometime before 330 BC Aristotle asserted that the elements of fire, air, earth, and water were not made of atoms, but were continuous. Aristotle considered the existence of a void, which was required by atomic theories, to violate physical principles. Change took place not by the rearrangement of atoms to make new structures, but by transformation of matter from what it was in potential to a new actuality. A piece of wet clay, when acted upon by a potter, takes on its potential to be an actual drinking mug. Aristotle has often been criticized for rejecting atomism, but in ancient Greece the atomic theories of Democritus remained "pure speculations, incapable of being put to any experimental test".[19][need quotation to verify][20][21][unbalanced opinion?] Aristotle theorized minima naturalia as the smallest parts into which a homogeneous natural substance (e.g., flesh, bone, or wood) could be divided and still retain its essential character. Unlike the atomism of Democritus, these Aristotelian "natural minima" were not conceptualized as physically indivisible. Instead, Aristotle's concept was rooted in his hylomorphic worldview, which held that every physical thing is a compound of matter (Greek hyle) and of an immaterial substantial form (Greek morphe) that imparts its essential nature and structure. For instance, a rubber ball - for a hylomorphist like Aristotle - would be rubber (matter) structured by spherical shape (form). Aristotle's intuition was that there is some smallest size beyond which matter could no longer be structured as flesh, or bone, or wood, or some other such organic substance that for Aristotle (living before the invention of the microscope) could be considered homogeneous. For instance, if flesh were divided beyond its natural minimum, what would be left might be a large amount of the element water, and smaller amounts of the other elements. But whatever water or other elements were left, they would no longer have the "nature" of flesh: in hylomorphic terms, they would no longer be matter structured by the form of flesh; instead the remaining water, e.g., would be matter structured by the form of water, not by the form of flesh. Later ancient atomism[edit] Epicurus (341–270 BCE) studied atomism with Nausiphanes who had been a student of Democritus. Although Epicurus was certain of the existence of atoms and the void, he was less sure we could adequately explain specific natural phenomena such as earthquakes, lightning, comets, or the phases of the Moon. [22] Few of Epicurus' writings survive, and those that do reflect his interest in applying Democritus' theories to assist people in taking responsibility for themselves and for their own happiness—since he held there are no gods around that can help them. (Epicurus regarded the role of gods as exemplifying moral ideals.) Epicurus' ideas re-appear in the works of his Roman follower Lucretius (c. 99 BC – c. 55 BC), who wrote On the Nature of Things. This Classical Latin scientific work in poetic form illustrates several segments of Epicurean theory on how the universe came into its current stage; it shows that the phenomena we perceive are actually composite forms. The atoms and the void are eternal and in constant motion. Atomic collisions create objects, which are still composed of the same eternal atoms whose motion for a while is incorporated into the created entity. Lucretius also explains human sensations and meteorological phenomena in terms of atomic motion. Atomism and ethics[edit] Some later philosophers attributed the idea that man created gods and that gods did not create man to Democritus. For example, Sextus Empiricus noted: Some people think that we arrived at the idea of gods from the remarkable things that happen in the world. Democritus ... says that the people of ancient times were frightened by happenings in the heavens such as thunder, lightning, ..., and thought that they were caused by gods.[23] Three hundred years after Epicurus, Lucretius in his epic poem On the Nature of Things would depict him as the hero who crushed the monster Religion through educating the people in what was possible in atoms and what was not possible in atoms. However, Epicurus expressed a non-aggressive attitude characterized by his statement: "The man who best knows how to meet external threats makes into one family all the creatures he can; and those he can not, he at any rate does not treat as aliens; and where he finds even this impossible, he avoids all dealings, and, so far as is advantageous, excludes them from his life."[24] Indian atomism[edit] In ancient Indian philosophy, preliminary instances of atomism are found in the works of Vedic sage Aruni, who lived in the 8th century BCE, especially his proposition that "particles too small to be seen mass together into the substances and objects of experience" known as kaṇa.[25] Although kana refers to "particles" not atoms (paramanu), Some scholars such as Hermann Jacobi and Randall Collins have compared Aruni to Thales of Miletus in their scientific methodology, calling them both as "primitive physicists" or "proto-materialist thinkers".[26] Later, the Charvaka,[27][28] and Ajivika schools of atomism originated as early as the 7th century BCE.[29][30][31] Bhattacharya posits that Charvaka may have been one of several atheistic, materialist schools that existed in ancient India.[32][33]Kanada founded the Vaisheshika school of Indian philosophy that also represents the earliest Indian natural philosophy. The Nyaya and Vaisheshika schools developed theories on how kaṇas combined into more complex objects.[34] Several of these doctrines of atomism are, in some respects, "suggestively similar" to that of Democritus.[35] McEvilley (2002) assumes that such similarities are due to extensive cultural contact and diffusion, probably in both directions.[36] The Nyaya–Vaisesika school developed one of the earliest forms of atomism; scholars[who?] date the Nyaya and Vaisesika texts from the 9th to 4th centuries BCE. Vaisesika atomists posited the four elemental atom types, but in Vaisesika physics atoms had 25 different possible qualities, divided between general extensive properties and specific (intensive) properties. The Nyaya–Vaisesika atomists had elaborate theories of how atoms combine. In Vaisesika atomism, atoms first combine in pairs (dyads), and then group into trios of pairs (triads), which are the smallest visible units of matter.[37] The Buddhist atomists had very qualitative, Aristotelian-style atomic theory. According to ancient Buddhist atomism, which probably began developing before the 4th century BCE, there are four kinds of atoms, corresponding to the standard elements. Each of these elements has a specific property, such as solidity or motion, and performs a specific function in mixtures, such as providing support or causing growth. Like the Hindus, the Buddhists were able to integrate a theory of atomism with their theological presuppositions. Later Indian Buddhist philosophers, such as Dharmakirti and Dignāga, considered atoms to be point-sized, durationless, and made of energy. Some of the canonical texts make reference to matter and atoms (called paramāṇu, a term already used in Yajnavalkya, Lalitha Sahasranama and Yoga Sutra), including Pancastikayasara, Kalpasutra and Tattvarthasutra.[&