democritus experiment on atoms

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Democritus, known in antiquity as the ‘laughing philosopher’ because of his emphasis on the value of ‘cheerfulness,’ was one of the two founders of ancient atomist theory. He elaborated a system originated by his teacher Leucippus into a materialist account of the natural world. The atomists held that there are smallest indivisible bodies from which everything else is composed, and that these move about in an infinite void. Of the ancient materialist accounts of the natural world which did not rely on some kind of teleology or purpose to account for the apparent order and regularity found in the world, atomism was the most influential. Even its chief critic, Aristotle, praised Democritus for arguing from sound considerations appropriate to natural philosophy.

1. Life and Works

2. atomist doctrine, 3. theory of perception, 4. the soul and the nature of living things, 5. theory of knowledge, 6. indivisibility and mathematics, 8. anthropology, other internet resources, related entries.

According to ancient reports, Democritus was born about 460 BCE (thus, he was a younger contemporary of Socrates) and was a citizen of Abdera, although some reports mention Miletus. As well as his associate or teacher Leucippus, Democritus is said to have known Anaxagoras, and to have been forty years younger than the latter (DK 68A1). A number of anecdotes concern his life, but their authenticity is uncertain.

The work of Democritus has survived only in secondhand reports, sometimes unreliable or conflicting: the reasoning behind the positions taken often needs to be reconstructed. Much of the best evidence is that reported by Aristotle, who regarded him as an important rival in natural philosophy. Aristotle wrote a monograph on Democritus, of which only a few passages quoted in other sources have survived. Democritus seems to have taken over and systematized the views of Leucippus, of whom little is known. Although it is possible to distinguish some contributions as those of Leucippus, the overwhelming majority of reports refer either to both figures, or to Democritus alone; the developed atomist system is often regarded as essentially Democritus’.

Diogenes Laertius lists a large number of works by Democritus on many fields, including ethics, physics, mathematics, music and cosmology. Two works, the Great World System and the Little World System (see the entry on doxography of ancient philosophy ), are sometimes ascribed to Democritus, although Theophrastus reports that the former is by Leucippus (DK 68A33). There is more uncertainty concerning the authenticity of the reports of Democritus’ ethical sayings. Two collections of sayings are recorded in the fifth-century anthology of Stobaeus, one ascribed to Democritus and another ascribed to an otherwise unknown philosopher ‘Democrates’. DK accepts both as relating to Democritus, but the authenticity of sayings in both collections is a matter of scholarly discussion, as is the relationship between Democritus’ atomism and his ethics.

Ancient sources describe atomism as one of a number of attempts by early Greek natural philosophers to respond to the challenge offered by Parmenides. Despite occasional challenges (Osborne 2004), this is how its motivation is generally interpreted by scholars today. Although the exact interpretation of Parmenides is disputed, he was taken to have argued that change is merely illusory because of some absurdities inherent in the idea of ‘what is not’. In response, Leucippus and Democritus, along with other Presocratic pluralists such as Empedocles and Anaxagoras, developed systems that clarified how change does not require that something should come to be from nothing. These responses to Parmenides suppose that there are multiple unchanging material principles, which persist and merely rearrange themselves to form the changing world of appearances. In the atomist version, these unchanging material principles are indivisible particles, the atoms. The idea that there is a lower limit to divisibility is sometimes taken as an answer to Zeno’s paradoxes about the impossibility of traversing infinitely divisible magnitudes (Hasper 2006). Reconstructions offered by Wardy (1988) and Sedley (2008) argue, instead, that atomism was developed as a response to Parmenidean arguments.

The atomists held that there are two fundamentally different kinds of realities composing the natural world, atoms and void. Atoms, from the Greek adjective atomos or atomon , ‘indivisible,’ are infinite in number and various in size and shape, and perfectly solid, with no internal gaps. They move about in an infinite void, repelling one another when they collide or combining into clusters by means of tiny hooks and barbs on their surfaces, which become entangled. Other than changing place, they are unchangeable, ungenerated and indestructible. All changes in the visible objects of the world of appearance are brought about by relocations of these atoms: in Aristotelian terms, the atomists reduce all change to change of place. Macroscopic objects in the world that we experience are really clusters of these atoms; changes in the objects we see—qualitative changes or growth, say—are caused by rearrangements or additions to the atoms composing them. While the atoms are eternal, the objects compounded out of them are not. Clusters of atoms moving in the infinite void come to form kosmoi or worlds as a result of a circular motion that gathers atoms up into a whirl, creating clusters within it (DK 68B167); these kosmoi are impermanent. Our world and the species within it have arisen from the collision of atoms moving about in such a whirl, and will likewise disintegrate in time.

In supposing that void exists, the atomists deliberately embraced an apparent contradiction, claiming that ‘what is not’ exists. Apparently addressing an argument by Melissus, a follower of Parmenides, the atomists paired the term for ‘nothing’ with what it negates, ‘thing,’ and claimed that—in a phrase typical of the atomists—the one ‘no more’ exists than the other (DK 67A6). Schofield (2002) argues that this particular phrase originated with Democritus and not his teacher Leucippus. By putting the full (or solid) and the void ontologically on a par, the atomists were apparently denying the impossibility of void. Void they considered to be a necessary condition for local motion: if there were no unoccupied places, where could bodies move into? Melissus had argued from the impossibility of void to the impossibility of motion; the atomists apparently reasoned in reverse, arguing from the fact that motion exists to the necessity for void space to exist (DK 67A7). It has been suggested that Democritus’ conception of void is that of the (temporarily) unfilled regions between atoms rather than a concept of absolute space (Sedley 1982). Void does not impede the motion of atoms because its essential quality is that of ‘yielding,’ in contrast to the mutual resistance of atoms. Later atomist accounts attest that this ‘yielding’ explains the tendency of bodies to drift into emptier spaces, driven out by collision from more densely packed regions (Lucretius DRN 6.906–1089).

Some controversy surrounds the properties of the atoms. They vary in size: one report—which some scholars question—suggests that atoms could, in principle, be as large as a cosmos, although at least in this cosmos they all seem to be too small to perceive (DK 68A47). They can take on an infinite variety of shapes: there are reports of an argument that there is ‘no more’ reason for the atoms to be one shape than another. Many kinds of atoms can interlock with one another because of their irregular shapes and hooks at their surface, accounting for the cohesiveness of some compounds. It is not clear whether the early atomists regarded atoms as conceptually indivisible or merely physically indivisible (Furley 1967). The idea that there is a smallest possible magnitude seems to suggest that this is the lower limit of size for atoms, although notions like being in contact or having shape seem to entail that even the smallest atoms have parts in some sense, if only mathematically or conceptually.

There are conflicting reports on whether atoms move in a particular direction as a result of their weight: a number of scholars have tried to reconcile these by supposing that weight is not intrinsic to the atoms, but is a result of the centripetal tendencies set up in the cosmic whirl (cf. O’Brien 1981; Furley 1989, pp. 91–102). Atoms may have an inherent tendency to a kind of vibratory motion, although the evidence for this is uncertain (McDiarmid 1958). However, their primary movement seems to result from collision with other atoms, wherein their mutual resistance or antitupia causes them to move away from one another when struck. Democritus is criticized by Aristotle for supposing that the sequence of colliding atoms has no beginning, and thus for not offering an explanation of the existence of atomic motion per se , even though the prior collision with another atom can account for the direction of each individual atomic motion (see O’Keefe 1996). Although the ancient atomists are often compared to modern ‘mechanistic’ theories, Balme warned of the danger of assuming that the atomists share modern ideas about the nature of atomic motion, particularly the idea that motion is inertial (Balme 1941).

According to different reports, Democritus ascribed the causes of things to necessity, and also to chance. Probably the latter term should be understood as ‘absence of purpose’ rather than a denial of necessity (Barnes 1982, pp. 423–6). Democritus apparently recognized a need to account for the fact that the disorderly motion of individual distinct atoms could produce an orderly cosmos in which atoms are not just randomly scattered, but cluster to form masses of distinct types. He is reported to have relied on a tendency of ‘like to like’ which exists in nature: just as animals of a kind cluster together, so atoms of similar kinds cluster by size and shape. He compares this to the winnowing of grains in a sieve, or the sorting of pebbles riffled by the tide: it is as if there were a kind of attraction of like to like (DK 68B164). Although this claim has been interpreted differently (e.g. Taylor 1999b p. 188), it seems to be an attempt to show how an apparently ordered arrangement can arise automatically, as a byproduct of the random collisions of bodies in motion (Furley 1989, p. 79). No attractive forces or purposes need be introduced to explain the sorting by the tide or in the sieve: it is probable that this is an attempt to show how apparently orderly effects can be produced without goal-directioned forces or purpose.

Democritus regards the properties of atoms in combination as sufficient to account for the multitude of differences among the objects in the world that appears to us. Aristotle cites an analogy to the letters of the alphabet, which can produce a multitude of different words from a few elements in combinations; the differences all stem from the shape ( schêma ) of the letters, as A differs from N; by their arrangement ( taxis ), as AN differs from NA; and by their positional orientation ( thesis ), as N differs from Z (DK 67A6). These terms are Aristotle’s interpretation of Democritus’ own terminology, which has a more dynamic sense (Mourelatos 2004). This passage omits differences of size, perhaps because it is focused on the analogy to letters of the alphabet: it is quite clear from other texts that Democritus thinks that atoms also differ in size.

He famously denies that perceptible qualities other than shape and size (and, perhaps, weight) really exist in the atoms themselves: one direct quotation surviving from Democritus claims that ‘by convention sweet and by convention bitter, by convention hot, by convention cold, by convention color; but in reality atoms and void’ (DK 68B9, trans. Taylor 1999a). There are different accounts of this distinction. Furley argues that the translation ‘convention’ should not be taken to suggest that there is anything arbitrary about the perception of certain colors, say: the same configuration of atoms may be regularly associated with a given color (Furley 1993; cf. Barnes 1982, pp. 370–7). What Democritus rejects with the label ‘merely conventional’ is, perhaps, the imputation of the qualities in question to the atoms, or perhaps even to macroscopic bodies. Mourelatos (2005) draws the contrast as that between intrinsic and relational properties.

While several reports of Democritus’ view, apparently direct quotations, mention exclusively sensible qualities as being unreal, a report of Plutarch includes in the list of things that exist only by convention the notion of ‘combination’ or sunkrisis . If this report is genuinely Democritean, it would broaden the scope of the claim considerably: the idea that any combination—by which he presumably means any cluster of atoms—is ‘unreal’ or merely ‘conventional’ suggests that Democritus is drawing a more radical distinction than that between sensible and nonsensible qualities. The implication would be that anything perceived, because it is a perception of combinations of atoms and not atoms themselves, would be suspect, not merely the qualia experienced by means of individual sense organs. One report indeed attributes to Democritus a denial that two things could become one, or vice versa (DK 68A42), thus suggesting that combinations are regarded as conventional.

Commentators differ as to the authenticity of Plutarch’s report. As the word sunkrisis does not occur in other reports, Furley (following Sandbach) suggests that it is most likely an error for pikron , ‘bitter’ which occurs instead in another report. However, Furley concedes that Plutarch at least understands the earliest atomists to be committed to the view that all combinations of atoms, as much as sensible qualities, should be understood as conventional rather than real (Furley 1993 pp. 76–7n7). This would suggest that everything at the macroscopic level—or, strictly, everything available to perception—is regarded as unreal. The ontological status of arrangement or combination of atoms for Democritus is a vexed question, that affects our understanding of his metaphysics, his historical relationship to Melissus, and the similarity of his views to the modern primary-secondary quality distinction (Wardy 1988; Curd 1998; Lee 2005; Mourelatos 2005; Pasnau 2007). If we take the ‘conventionality’ thesis to be restricted to sensible qualities, there is still an open question about Democritus’ reason for denying their ‘reality’ (Wardy 1988; O’Keefe 1997; Ganson 1999).

Democritus’ theory of perception depends on the claim that eidôla or images, thin layers of atoms, are constantly sloughed off from the surfaces of macroscopic bodies and carried through the air. Later atomists cite as evidence for this the gradual erosion of bodies over time. These films of atoms shrink and expand; only those that shrink sufficiently can enter the eye. It is the impact of these on our sense organs that enables us to perceive. Visible properties of macroscopic objects, like their size and shape, are conveyed to us by these films, which tend to be distorted as they pass through greater distances in the air, since they are subject to more collisions with air atoms. A different or complementary account claims that the object seen impresses the air by the eidôla , and the compacted air thus conveys the image to the eye (DK 68A135; Baldes 1975). The properties perceived by other senses are also conveyed by contact of some kind. Democritus’ theory of taste, for example, shows how different taste sensations are regularly produced by contact with different shapes of atoms.

Theophrastus, who gives us the most thorough report of Democritus’ theory, criticizes it for raising the expectation that the same kinds of atoms would always cause similar appearances. However, it may be that most explanations are directed towards the normal case of a typical observer, and that a different account is given as to the perceptions of a nontypical observer, such as someone who is ill. Democritus’ account why honey sometimes tastes bitter to people who are ill depends on two factors, neither of which undercut the notion that certain atomic shapes regularly affect us in a given way. One is that a given substance like honey is not quite homogeneous, but contains atoms of different shapes. While it takes its normal character from the predominant type of atom present, there are other atom-types present within. The other is that our sense-organs need to be suitably harmonized to admit a given atom-type, and the disposition of our passageways can be affected by illness or other conditions. Thus someone who is ill may become unusually receptive to an atom-type that is only a small part of honey’s overall constitution.

Other observed effects, however, require a theory whereby the same atoms can produce different effects without supposing that the observer has changed. The change must then occur in the object seen. The explanation of color seems to be of this variety: Aristotle reports that things acquire their color by ‘turning,’ tropê ( GC 1.2, 315b34). This is the Democritean term that Aristotle had translated as ‘position,’ thesis , i.e. one of the three fundamental ways in which atoms can alter and thus appear differently to us. Aristotle gives this as the reason why color is not ascribed to the atoms themselves. Lucretius’ account of why color cannot belong to atoms may help clarify the point here. We are told that if the sea’s atoms were really blue, they could not undergo some change and look white ( DRN 2.774–5), as when we observe the sea’s surface changing from blue to white. This seems to assume that, while an appearance of a property P can be produced by something that is neither P nor not-P, nonetheless something P cannot appear not-P. Since atoms do not change their intrinsic properties, it seems that change in a relational property, such as the relative position of atoms, is most likely to be the cause of differing perceptions. In the shifting surface of the sea or the flutter of the pigeon with its irridescent neck, it is evident that the parts of the object are moving and shifting in their positional relations.

By ascribing the causes of sensible qualities to relational properties of atoms, Democritus forfeits the prima facie plausibility of claiming that things seem P because they are P. Much of Theophrastus’ report seems to focus on the need to make it plausible that a composite can produce an appearance of properties it does not intrinsically possess. Democritus is flying in the face of at least one strand of commonsense when he claims that textures produce the appearance of hot or cold, impacts cause colour sensations. The lists of examples offered, drawing on commonsense associations or anecdotal experience, are attempts to make such claims persuasive. Heat is said to be caused by spherical atoms, because these move freely: the commonsense association of quick movement with heating may be employed here. Betegh (2020) suggests that larger void spaces are directly associated with heating, rather than that rarefaction indirectly causes heat by allowing freer and more frequent atomic motion.

Aristotle sometimes criticizes Democritus for claiming that visible, audible, olfactory and gustatory sensations are all caused by touch (DK 68A119). Quite how this affects the account of perception is not clear, as the sources tells us little about how touch is thought to work. Democritus does not, however, seem to distinguish between touch and contact, and may take it to be unproblematic that bodies communicate their size, shape and surface texture by physical impact.

In common with other early ancient theories of living things, Democritus seems to have used the term psychê to refer to that distinctive feature of living things that accounts for their ability to perform their life-functions. According to Aristotle, Democritus regarded the soul as composed of one kind of atom, in particular fire atoms. This seems to have been because of the association of life with heat, and because spherical fire atoms are readily mobile, and the soul is regarded as causing motion. Democritus seems to have considered thought to be caused by physical movements of atoms also. This is sometimes taken as evidence that Democritus denied the survival of a personal soul after death, although the reports are not univocal on this.

One difficulty faced by materialist theories of living things is to account for the existence and regular reproduction of functionally adapted forms in the natural world. Although the atomists have considerable success in making it plausible that a simple ontology of atoms and void, with the minimal properties of the former, can account for a wide variety of differences in the objects in the perceptible world, and also that a number of apparently orderly effects can be produced as a byproduct of disorderly atomic collisions, the kind of functional organization found in organisms is much harder to explain.

Democritus seems to have developed a view of reproduction according to which all parts of the body contribute to the seed from which the new animal grows, and that both parents contribute seed (DK 68A141; 143). The theory seems to presuppose that the presence of some material from each organ in the seed accounts for the development of that organ in the new organism. Parental characteristics are inherited when the contribution of one or other parent predominates in supplying the appropriate part. The offspring is male or female according to which of the two seeds predominates in contributing material from the genitals. In an atomist cosmos, the existence of particular species is not considered to be eternal. Like some other early materialist accounts, Democritus held that human beings arose from the earth (DK 68A139), although the reports give little detail.

One report credits Democritus and Leucippus with the view that thought as well as sensation are caused by images impinging on the body from outside, and that thought as much as perception depends on images (DK 67A30). Thought as well as perception are described as changes in the body. Democritus apparently recognized that his view gives rise to an epistemological problem: it takes our knowledge of the world to be derived from our sense experience, but the senses themselves not to be in direct contact with the nature of things, thus leaving room for omission or error. A famous fragment may be responding to such a skeptical line of thought by accusing the mind of overthrowing the senses, though those are its only access to the truth (DK68B125). Other passages talk of a gap between what we can perceive and what really exists (DK 68B6–10; 117). But the fact that atoms are not perceptible means that our knowledge of their properties is always based on analogy from the things of the visible world. Moreover, the senses report properties that the atoms don’t really possess, like colors and tastes. Thus the potential for doubt about our knowledge of the external world looms large.

Later philosophers adapted a Democritean phrase ou mallon or ‘no more’ in the argument that something that seems both P and not-P is ‘no more’ P than not-P. Arguments of this form were used for sceptical purposes, citing the conflicting evidence of the senses in order to raise concern about our knowledge of the world (de Lacy 1958). Democritus does not seem to be pursuing a consistently skeptical program, although he does express concern about the basis for our knowledge.

The idea that our knowledge is based on the reception of images from outside us is employed in Democritus’ discussion of the gods, wherein it is clear that our knowledge of the gods comes from eidôla or giant films of atoms with the characteristics we attribute to the gods, although Democritus denies that they are immortal. Some scholars take this to be a deflationary attack on traditional theology as based on mere images (Barnes 1982, pp. 456–61), but others suppose that the theory posits that these eidôla are really living beings (Taylor 1999a, pp. 211–6). Although atomism is often identified as an atheist doctrine in later times, it is not clear whether this is really Democritus’ view.

The reasons for supposing that there are indivisible magnitudes apparently stem from Zeno of Elea’s account of paradoxes that arise if extension is understood to be infinitely divisible, i.e. composed of an infinite number of parts. The atomists may have sought to avoid these paradoxes by supposing that there is a limit to divisibility.

It is not clear, however, in what sense the atoms are said to be indivisible, and how the need for smallest magnitudes is related to the claim that atoms are indivisible. Furley suggests that the atomists may not have distinguished between physical and theoretical indivisibility of the atoms (Furley 1967, p. 94). The physical indivisibility of the atoms seems to be independent of the argument for indivisible magnitudes, since the solidity of atoms—the fact that there is no void within them—is said to be the reason why they cannot be split. The existence of void space between atoms is cited as the reason why they can be separated: one late source, Philoponus, even suggests that atoms could never actually touch, lest they fuse (DK 67A7). Whether or not Democritus himself saw this consequence, it seems that atoms are taken to be indivisible whatever their size. Presumably, though, there is a smallest size of atom, and this is thought to be enough to avoid the paradoxes of infinite divisibility.

A reductio ad absurdum argument reported by Aristotle suggests that the atomists argued from the assumption that, if a magnitude is infinitely divisible, nothing prevents it actually having been divided at every point. The atomist then asks what would remain: if the answer is some extended particles, such as dust, then the hypothesized division has not yet been completed. If the answer is nothing or points, then the question is how an extended magnitude could be composed from what does not have extension (DK 68A48b, 123).

Democritus is also said to have contributed to mathematics, and to have posed a problem about the nature of the cone. He argues that if a cone is sliced anywhere parallel to its base, the two faces thus produced must either be the same in size or different. If they are the same, however, the cone would seem to be a cylinder; but if they are different, the cone would turn out to have step-like rather than continuous sides. Although it is not clear from Plutarch’s report how (or if) Democritus solved the problem, it does seem that he was conscious of questions about the relationship between atomism as a physical theory and the nature of mathematical objects.

The reports concerning Democritus’ ethical views pose a number of interpretative problems, including the difficulty of deciding which fragments are genuinely Democritean (see above, section 1). In contrast to the evidence for his physical theories, many of the ethical fragments are lists of sayings quoted without context, rather than critical philosophical discussions of atomist views. Many seem like commonsense platitudes that would be consistent with quite different philosophical positions. Thus, despite the large number of ethical sayings, it is difficult to construct a coherent account of his ethical views. Annas notes the Socratic character of a number of the sayings, and thinks there is a consistent theme about the role of one’s own intellect in happiness (Annas 2002). The sayings contain elements that can be seen as anticipating the more developed ethical views of Epicurus (Warren 2002).

It is also a matter of controversy whether any conceptual link can be found between atomist physics and the ethical commitments attributed to Democritus. Vlastos argued that a number of features of Democritus’ naturalistic ethics can be traced to his materialist account of the soul and his rejection of a supernatural grounding for ethics (Vlastos 1975). Taylor is more sceptical about the closeness of the connection between Democritus’ ethical views and his atomist physics (Taylor 1999a, pp. 232–4).

The reports indicate that Democritus was committed to a kind of enlightened hedonism, in which the good was held to be an internal state of mind rather than something external to it (see Hasper 2014). The good is given many names, amongst them euthymia or cheerfulness, as well as privative terms, e.g. for the absence of fear. Some fragments suggest that moderation and mindfulness in one’s pursuit of pleasures is beneficial; others focus on the need to free oneself from dependence on fortune by moderating desire. Several passages focus on the human ability to act on nature by means of teaching and art, and on a notion of balance and moderation that suggests that ethics is conceived as an art of caring for the soul analogous to medicine’s care for the body (Vlastos 1975, pp. 386–94). Others discuss political community, suggesting that there is a natural tendency to form communities.

Although the evidence is not certain, Democritus may be the originator of an ancient theory about the historical development of human communities. In contrast to the Hesiodic view that the human past included a golden age from which the present day is a decline, an alternative tradition that may derive from Democritus suggests that human life was originally like that of animals; it describes the gradual development of human communities for purposes of mutual aid, the origin of language, crafts and agriculture. Although the text in question does not mention Democritus by name, he is the most plausible source (Cole 1967; Cartledge 1997).

If Democritus is the source for this theory, it suggests that he took seriously the need to account for the origin of all aspects of the world of our experience. Human institutions could not be assumed to be permanent features or divine gifts. The explanations offered suggest that human culture developed as a response to necessity and the hardships of our environment. It has been suggested that the sheer infinite size of the atomist universe and thus the number of possible combinations and arrangements that would occur by chance alone are important in the development of an account that can show how human institutions arise without assuming teleological or theological origins (Cole 1967). Although here, as on other questions, the evidence is less than certain, it is plausible that Democritus developed a powerful and consistent explanation of much of the natural world from a very few fundamentals.

For the reception and subsequent history of Democritean atomism, see the related entry on ancient atomism.

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• –––, 1997, ‘The Ontological Status of Sensible Qualities for Democritus and Epicurus,’ Ancient Philosophy , 17: 119–34.
• Osborne, Catherine, 2004, Presocratic Philosophy: A Very Short Introduction , Oxford: Oxford University Press.
• Pasnau, Robert, 2007, ‘Democritus and Secondary Qualities,’ Archiv für Geschichte der Philosophie , 89: 99–121.
• Schofield, Malcolm, 2002, ‘Leucippus, Democritus and the ou mallon Principle: An Examination of Theophrastus Phys. Op. Fr. 8,’ Phronesis , 47(3): 253–63.
• Sedley, David, 1982, ‘Two Conceptions of Vacuum,’ Phronesis , 27: 175–93.
• Sedley, David, 2008, ‘Atomism’s Eleatic Roots,’ in Patricia Curd and Daniel W. Graham (eds.), The Oxford Handbook of Presocratic Philosophy , Oxford: Oxford University Press, 305–332.
• Sorabji, Richard, 1983, Time, Creation and the Continuum , London: Duckworth.
• Taylor, C.C.W., 2007, ‘Nomos and Phusis in Democritus and Plato,’ Social Philosophy and Policy , 24 (2): 1–20.
• Vlastos, G., 1975, ‘Ethics and physics in Democritus,’ in D.J. Furley and R.E. Allen (eds.), Studies in Presocratic Philosophy (Volume 2: Eleatics and Pluralists ), London: Routledge and Kegan Paul, pp. 381–408.
• Wardy, Robert, 1988, ‘Eleatic Pluralism,’ Archiv für Geschichte der Philosophie , 70: 125–46.
• Warren, James, 2002, Epicurus and Democritean Ethics: An Archaeology of Ataraxia , Cambridge: Cambridge University Press.
• Zilioli, Ugo (ed.), 2021, Atomism in Philosophy: A History from Antiquity to the Present , London: Bloomsbury.

How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

• Translation of S. Luria’s Demokrit , by C.C.W. Taylor (must be registered at academia.edu).

atomism: ancient | doxography of ancient philosophy | Epicurus | Leucippus | Lucretius | -->Melissus --> | Parmenides | Zeno of Elea | Zeno of Elea: Zeno’s paradoxes

Acknowledgments

I wish to thank the ancient philosophy editor John Cooper, A.P.D. Mourelatos and Tim O’Keefe for helpful comments and suggestions.

Copyright © 2023 by Sylvia Berryman < sberrym @ interchange . ubc . ca >

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Ancient physics: How Democritus predicted the atom

Credit: vinap via Adobe Stock / Public Domain via Wikimedia

• The idea of the atom goes as far back as the ancient Greek philosopher Democritus in about 400 B.C.E.
• This led to his “theory of eidôla” to explain how our minds create the illusion of reality.
• Democritus was one of the first determinists, arguing that a world made only of atoms and controlled by the laws of physics left no room for free will.

Philosophers love “The Matrix”.

It’s the perfect introduction to the ideas of big names such as Plato and Descartes but with leather trench coats, bullet time, and a brooding Keanu Reeves. One of the most memorable moments in the movie comes near the end when the protagonist, Neo, finally understands the Matrix for the illusionary simulation that it is. Now, he can see the numbers underpinning everything. He can see the source code of the world.

With only the slightest of modifications, Neo’s epiphany is no science fiction at all. This is how the world is made. But, where Neo saw green, floating numbers, we now know the universe is actually made up of tiny, imperceptible objects. Rather than code, we have atoms—the building blocks of everything there is, ever was, and ever will be.

We know atoms exist thanks to scientists and electron microscopes, but the idea goes much further back than that. It goes back to the ancient Greeks. Their output was prodigious. Almost every discipline you can study, the Greeks turned their minds to first. Pythagoras laid the foundation for math and geometry, Aristotle contemplated biology and physics, Plato thought about governance, Herodotus was a historian, and Hippocrates gave doctors his eponymous oath. But one of the most ingenious “firsts” must come with the atomists, like Democritus or Epicurus.

It’s odd to think that millennia ago, a few bearded men in togas, strolling around a sun-bleached agora, used philosophy to establish the fundamental fabric of the universe.

Although the idea of “the atom” had been floating around the Peloponnese for a while, Democritus was the first to articulate it fully. He argued that atoms must exist because the alternative is sheer nonsense. If we could constantly divide or cut a thing into two then we would go on forever. We’d get smaller and smaller all the way to infinity, and there’d be no end point. But the universe can’t be built without foundations. Nothing can come from nothing. So, there must be a fundamental unit to the world from which everything else is made, and for this, Democritus coined the term “atom” (which literally means uncuttable, although 20th Century scientists learned how to split one, rather ruining the definition).

The question now facing Democritus was how these basic, imperceptible atoms came to make the objects we all see, touch, and love. He noted how, when we look at the world around us, we can see it constantly changing, shifting, dying, and growing. The world flows. So atoms, which make up everything there is, must themselves be moving. They can’t just be inert or still.

Democritus argued that atoms come together in various combinations, and then emit something called an “ eidôla. ” These composite blobs of atoms radiate eidôla outward, like ripples in water. The eidôla are then picked up by us as the subjective experiencer and we translate this atomic radiation into ideas or sensations.

For example, let’s imagine a group of atoms come together and, with a special wiggle, emit their eidôla . This flies through the space (or “void,” as Democritus called it) to our eyes. Our eyes then whizz this eidôla along to our understanding, where it’s converted into “blue” or “round” or “big.”

There were two big implications to Democritus’ theory.

First, the world as we know it doesn’t actually exist. Just like the code in the Matrix, the world is really just incomprehensible atoms. Our minds create “reality” out of these atoms, and everything is just an illusion we play on ourselves.

Second, the world is entirely made up of atoms. The tree outside, your pet turtle, your feeling of love, and even the mind that processes eidôla are all made up of atoms.

The upshot of this is that Democritus was one of the first “determinists” in that he thought there could be no free will or choice. We’re all just marbles, bouncing around to the laws of physics.

We might think this a pretty depressing place to finish, yet Democritus was actually known as “the laughing philosopher.” He simply refused to take anything seriously. If reality was ultimately the invented story of our minds, and the universe was just physical laws, what’s the point in getting wound up by things? Why stress about that email from your boss, or that mean thing a friend said when there’s nothing we can do anyway? If the world is an illusion, and a boringly scripted one at that, why not laugh?

The first “atomist,” Democritus, of course got a lot wrong, but it’s remarkable how much he got right. By reflecting on reality long enough, he came to conclusions that scientists proved millennia later. If nothing else, he offers a shining example of the power of contemplation.

Jonny Thomson teaches philosophy in Oxford. He runs a popular Instagram account called Mini Philosophy (@ philosophyminis ). His first book is Mini Philosophy: A Small Book of Big Ideas .

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Lesson 1:  In Search of the Atom

Part a: democritus to dalton.

Part 1a: Democritus to Dalton Part 1b: The Inside Story of the Atom Part 1c: Subatomic Particles

What is Matter Made Of?

A Philosopher’s View

Dalton’s atomic theory.

• All matter is composed of extremely small particles called atoms.
• Atoms cannot be subdivided, created, or destroyed.
• Atoms of a given element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties.
• Atoms of different elements can combine in simple whole number ratios to form chemical compounds.
• In chemical reactions, atoms are combined, separated, or rearranged.

Different Types of Atoms

The Law of Constant Composition

The Law of Multiple Proportions

The Law of Conservation of Mass

Moving Beyond Dalton

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Democritus' atomic model

Key principles of democritus' atomic model, indivisibility of atoms, diversity of shapes and sizes, empty space (void or "kenón"), eternal movement, mechanical nature of the universe, infinity, non-creation and eternity of atoms, evolution of the democritus model, philosophical atomism.

Atomism is a natural physical and philosophical theory, according to which sensually perceived (material) things consist of chemically indivisible particles - atoms. It has its origins in ancient Greek philosophy. It was mainly developed in the field of philosophy and science of the Middle Ages and Modern Times.

Leucippus and Democritus

Atoms (Leucippus and Democritus)

Our senses suggest that matter is continuous. The air that surrounds us, for example, feels like a continuous fluid. (We do not feel bombarded by individual particles in the air.) The water we drink looks like a continuous fluid. (We can take a glass of water, divide it in halves, and repeat this process again and again, without appearing to reach the point at which it is impossible to divide it one more time.)

Because our senses suggest that matter is continuous, it isn't surprising that the debate about the existence of atoms goes back as far as we can trace and continued well into this century. The first proponents of an atomic theory were the Greek philosophers Leucippus and Democritus who proposed the following model in the fifth century B.C.

1. Matter is composed of atoms separated by empty space through which the atoms move.

2. Atoms are solid, homogeneous, indivisible, and unchangeable.

3. All apparent changes in matter result from changes in the groupings of atoms.

4. There are different kinds of atoms that differ in size and shape.

5. The properties of matter reflect the properties of the atoms the matter contains.

This model attracted few supporters among later generations of Greek philosophers. Aristotle , in particular, refused to accept the idea that the natural world could be reduced to a random assortment of atoms moving through a vacuum.

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Democritus summary

Democritus , (born c. 460—died c. 370 bc ), Greek philosopher. Though only a few fragments of his work survive, he was apparently the first to describe invisible “atoms” as the basis of all matter. His atoms—indestructible, indivisible, incompressible, uniform, and differing only in size, shape, and motion—anticipated with surprising accuracy those discovered by 20th-century scientists. For his amusement at human foibles, he has been called “the Laughing Philosopher.” See also atomism .

Early Ideas about Matter: From Democritus to Dalton

by Anthony Carpi, Ph.D.

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Did you know that some ancient Greeks believed that all matter was made up of four substances: fire, air, water, and earth? They believed that rabbits were soft because they had more water than earth. Although this idea seems silly now, it contains a fundamental principle of atomic theory: that matter is made up of a small number of fundamental elements.

Early humans easily distinguished between materials that were used for making clothes, those that could be shaped into tools, or those that were good to eat. Then they gave these things the names, such as "fur," "stone," or "rabbit." However, these people did not have our current understanding of the substances that made up those objects. Empedocles , a Greek philosopher and scientist who lived on the south coast of Sicily between 492 BCE and 432 BCE, proposed one of the first theories that attempted to describe the things around us. Empedocles argued that all matter was composed of four elements: fire, air, water, and earth. The ratio of these four elements affected the properties of the matter. Stone was thought to contain a high amount of earth, while a rabbit was thought to have a higher ratio of both water and fire, thus making it soft and giving it life.

Empedocles's theory was quite popular, but it had a number of problems. For example, regardless of how many times you break a stone in half, the pieces never resemble any of the core elements of fire, air, water, or earth. Despite these problems, Empedocles 's theory was an important development in scientific thinking because it was among the first to suggest that some substances that looked like pure materials, like stone, were actually made up of a combination of different "elements."

• The atom is proposed

A few decades after Empedocles , Democritus (460 BCE - 370 BCE), who was also Greek, developed a new theory of matter that attempted to overcome the problems of his predecessor. Democritus's ideas were based on reasoning rather than science, and drew on the teachings of two Greek philosophers who came before him: Leucippus and Anaxagoras . Democritus knew that if you took a stone and cut it in half, each half had the same properties as the original stone. He reasoned that if you continued to cut the stone into smaller and smaller pieces, at some point you would reach a piece so tiny that it could no longer be divided. Democritus called these infinitesimally small pieces of matter atomos , meaning 'indivisible'. He suggested that atomos were eternal and could not be destroyed. Democritus theorized that atomos were specific to the material that they made up, meaning that the atomos of stone were unique to stone and different from the atomos of other materials, such as fur. This was a remarkable theory that attempted to explain the whole physical world in terms of a small number of ideas.

Ultimately, though, Aristotle and Plato, two of the best-known philosophers of Ancient Greece, rejected the theories of Democritus . Aristotle accepted the theory of Empedocles , adding his own (incorrect) idea that the four core elements could be transformed into one another. Because of Aristotle's great influence, Democritus's theory would have to wait almost 2,000 years before being rediscovered.

In the 17 th and 18 th centuries CE , several key events helped revive the theory that matter was made of small, indivisible particles . In 1643, Evangelista Torricelli , an Italian mathematician and pupil of Galileo, showed that air had weight and was capable of pushing down on a column of liquid mercury (thus inventing the barometer). This was a startling finding. If air – this substance that we could not see, feel, or smell – had weight, it must be made of something physical. But how could something have a physical presence, yet not respond to human touch or sight? Daniel Bernoulli , a Swiss mathematician, proposed an answer. He developed a theory that air and other gases consist of tiny particles that are too small to be seen, and are loosely packed in an empty volume of space. The particles could not be felt because unlike a solid stone wall that does not move, the tiny particles move aside when a human hand or body moves through them. Bernoulli reasoned that if these particles were not in constant motion, they would settle to the ground like dust particles; therefore, he pictured air and other gases as loose collections of tiny billiard-ball-like particles that are continuously moving around and bouncing off one another.

• Law of Conservation of Mass

Many scientists were busy studying the natural world at this time. Shortly after Bernoulli proposed his theory , the Englishman Joseph Priestley began to experiment with red mercury calx in 1773. Mercury calx, a red solid stone, had been known and coveted for thousands of years because when it is heated, it appears to turn into mercury, a silver liquid metal. Priestley had observed that it does not just turn into mercury; it actually breaks down into two substances when it is heated, liquid mercury and a strange gas . Priestley carefully collected this gas in glass jars and studied it. After many long days and nights in the laboratory, Priestley said of the strange gas, "What surprised me more than I can well express was that a candle burned in this air with a remarkably vigorous flame." Not only did flames burn strongly in this gas, but a mouse placed in a sealed container of this gas lived for a longer period of time than a mouse placed in a sealed container of ordinary air. Priestley's discovery revealed that substances could combine together or break apart to form new substances with different properties. For example, a colorless, odorless gas could combine with mercury, a silver metal, to form mercury calx, a red mineral .

Priestley called the gas he discovered dephlogisticated air , but this name would not stick. In 1778, Antoine Lavoisier , a French scientist, conducted many experiments with dephlogisticated air and theorized that the gas made some substances acidic. He renamed Priestley's gas oxygen , from the Greek words that loosely translate as 'acid maker'. While Lavoisier's theory about oxygen and acids proved incorrect, his name stuck. Lavoisier knew from other scientists before him that acids react with some metals to release another strange and highly flammable gas called phlogiston . Lavoisier mixed the two gases, phlogiston and the newly renamed oxygen, in a closed glass container and inserted a match. He saw that phlogiston immediately burned in the presence of oxygen, and afterwards he observed droplets of water on the glass container. After careful testing, Lavoisier realized that the water was formed by the reaction of phlogiston and oxygen, and so he renamed phlogiston hydrogen , from the Greek words for 'water maker'.

Lavoisier also burned other substances such as phosphorus and sulfur in air, and showed that they combined with air to make new materials. These new materials weighed more than the original substances, and Lavoisier showed that the weight gained by the new materials was lost from the air in which the substances were burned. From these observations , Lavoisier established the Law of Conservation of Mass , which says that mass is not lost or gained during a chemical reaction .

Comprehension Checkpoint

• Modern atomic theory

Priestley, Lavoisier, and others had laid the foundations of the field of chemistry. Their experiments showed that some substances could combine with others to form new materials, other substances could be broken apart to form simpler ones, and a few key "elements" could not be broken down any further. But what could explain this complex set of observations? John Dalton , an exceptional British teacher and scientist, put together the pieces and developed the first modern atomic theory in 1803. To learn more about Priestley's and Lavoisier's experiments and how they formed the basis of Dalton's theories , try the interactive experiment Dalton's Playhouse , linked to below.

Interactive Animation: Dalton's Playhouse

Dalton made it a regular habit to track and record the weather in his hometown of Manchester, England. Through his observations of morning fog and other weather patterns, Dalton realized that water could exist as a gas that mixed with air and occupied the same space as air. Solids could not occupy the same space as each other; for example, ice could not mix with air. So what could allow water to sometimes behave as a solid and sometimes as a gas? Dalton realized that all matter must be composed of tiny particles . In the gas state, those particles floated freely around and could mix with other gases, as Bernoulli had proposed. But Dalton extended this idea to apply to all matter – gases, solids, and liquids . Dalton first proposed part of his atomic theory in 1803 and later refined these concepts in his classic 1808 paper A New System of Chemical Philosophy (which you can access through a link under the Resources tab).

All matter is composed of indivisible particles called atoms . Bernoulli, Dalton, and others pictured atoms as tiny billiard-ball-like particles in various states of motion. While this concept is useful to help us understand atoms, it is not correct as we will see in later modules on atomic theory linked to at the bottom of this module.

All atoms of a given element are identical; atoms of different elements have different properties. Dalton's theory suggested that every single atom of an element such as oxygen is identical to every other oxygen atom; furthermore, atoms of different elements, such as oxygen and mercury, are different from each other. Dalton characterized elements according to their atomic weight ; however, when isotopes of elements were discovered in the late 1800s, this concept changed.

Chemical reactions involve the combination of atoms, not the destruction of atoms. Atoms are indestructible and unchangeable, so compounds , such as water and mercury calx, are formed when one atom chemically combines with other atoms. This was an extremely advanced concept for its time; while Dalton's theory implied that atoms bonded together, it would be more than 100 years before scientists began to explain the concept of chemical bonding .

When elements react to form compounds, they react in defined, whole-number ratios . The experiments that Dalton and others performed showed that reactions are not random events; they proceed according to precise and well-defined formulas . This important concept in chemistry is discussed in more detail below.

Some of the details of Dalton's atomic theory require more explanation.

Elements: As early as 1660, Robert Boyle recognized that the Greek definition of element (earth, fire, air, and water) was not correct. Boyle proposed a new definition of an element as a fundamental substance, and we now define elements as fundamental substances that cannot be broken down further by chemical means . Elements are the building blocks of the universe . They are pure substances that form the basis of all of the materials around us. Some elements can be seen in pure form, such as mercury in a thermometer; some we see mainly in chemical combination with others, such as oxygen and hydrogen in water. We now know of approximately 116 different elements. Each of the elements is given a name and a one- or two-letter abbreviation. Often this abbreviation is simply the first letter of the element; for example, hydrogen is abbreviated as H, and oxygen as O. Sometimes an element is given a two-letter abbreviation; for example, helium is He. When writing the abbreviation for an element, the first letter is always capitalized and the second letter (if there is one) is always lowercase.

Atoms: A single unit of an element is called an atom . The atom is the most basic unit of matter , which makes up everything in the world around us. Each atom retains all of the chemical and physical properties of its parent element. At the end of the nineteenth century, scientists would show that atoms were actually made up of smaller, "subatomic" pieces, which smashed the billiard-ball concept of the atom (see our Atomic Theory I: The Early Days module).

Compounds: Most of the materials we come into contact with are compounds, substances formed by the chemical combination of two or more atoms of the elements. A single "particle" of a compound is called a molecule . Dalton incorrectly imagined that atoms "hooked" together to form molecules. However, Dalton correctly realized that compounds have precise formulas . Water, for example, is always made up of two parts hydrogen and one part oxygen. The chemical formula of a compound is written by listing the symbols of the elements together, without any spaces between them. If a molecule contains more than one atom of an element, a number is subscripted after the symbol to show the number of atoms of that element in the molecule. Thus the formula for water is H 2 O, never HO or H 2 O 2 .

• Law of Definite Proportions

The idea that compounds have defined chemical formulas was first proposed in the late 1700s by the French chemist Joseph Proust . Proust performed a number of experiments and observed that no matter how he caused different elements to react with oxygen, they always reacted in defined proportions. For example, two parts of hydrogen always reacts with one part oxygen when forming water; one part mercury always reacts with one part oxygen when forming mercury calx. Dalton used Proust's Law of Definite Proportions in developing his atomic theory .

The law also applies to multiples of the fundamental proportion, for example:

In both of these examples, the ratio of hydrogen to oxygen to water is 2 to 1 to 1. When reactants are present in excess of the fundamental proportions, some reactants will remain unchanged after the chemical reaction has occurred.

The story of the development of modern atomic theory is one in which scientists built upon the work of others to produce a more accurate explanation of the world around them. This process is common in science, and even incorrect theories can contribute to important scientific discoveries. Dalton, Priestley, and others laid the foundation of atomic theory, and many of their hypotheses are still useful. However, in the decades after their work, other scientists would show that atoms are not solid billiard balls, but complex systems of particles . Thus, they would smash apart a bit of Dalton's atomic theory in an effort to build a more complete view of the world around us.

Table of Contents

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A good question, with a fascinating history. I'll answer from the perspective of electronic materials in materials science. In short, In fact, we can even manipulate individual atoms for potentially useful things (more on this later)! But this was not always the case. One of the earliest records we have on the atom came from Democritus, an ancient Greek philosopher (others like Plato and Aristotle had similar trains of thought). Democritus had a thought experiment. The idea was if you took a material and divided it half, you would have a smaller but identical chunk. If you keep dividing your material, there should eventually be a point where you've reached the smallest representative element of your material. That element is the In fact "atom" is derived from the Greek word "atomos," which roughly translates to indivisible (it turns out there are even smaller components that make up an atom, but the name stuck; see ). It wasn't until much later in the 18th and 19th centuries that significant progress towards understanding the atom was made. Our understanding of the structure of the atom has vastly changed from the model John Dalton first proposed with the development and advancement of quantum mechanics. It is the interplay between theory (e.g., quantum mechanics) and experiment that let's us characterize and engineer materials at the atomic level. Both are part of a feedback loop where e.g., experiment confirms a theoretical prediction or theory explains what is observed experimentally. Read more about the history and how our understanding of the atom changed ) (several seminal experiments that contributed to this are described). The coolest part is the fact that , and even manipulate them! is the famous image of using a scanning tunneling microscope. Each dot you see is an . Read more and . (you might have heard of nanotechnology, for instance). For example, here at UCSB, there is active research on growing materials with atomically sharp interfaces. Here is an . Each of the balls you see corresponds to a or atom; the other elements are harder to see because they are smaller/lighter, though you might be able to see the >b>Al and if you squint hard enough). This material was carefully grown using a technique called , and is being studied for its rich physics and as the next big electronic material for things like your computer and phone. Hope this helps! Best,

Nowadays we can indeed see atoms using advanced technology, like . This technology allows us to observe, or even move an individual atom. Here is a picture of the silicon atoms that scientists see using STM:

We can't see them with our eyes because they're too small, but we can build machines that can see them. In particular, , so using an x-ray camera and shining x-rays through something with an orderly arrangement of atoms (like a crystal), we can see the atoms inside of it by seeing how the x-rays scatter.

Great question. At first, scientists were not sure about what matter looked like on a very small scale. Atoms were just a theory. But scientists made a lot of other theories in chemistry that fit with the idea that matter is made up of atoms. Even though we couldn't prove these theories, many of them were useful. For example, atoms can explain why chemicals always react in the same ratios, since these chemicals are made up of atoms that must group together in the same numbers every time. We can use the STM to see details smaller than one nanometer, including atoms. has some interesting images made using the STM. We even have machines that can arrange atoms in simple patterns--many early examples of this technology show atoms arranged to spell out words or company names, like and to return to the search form. 353 IMAGES Democritus by barron.jannet Democritus Atomic Model Experiment Ancient physics: How Democritus predicted the atom democritus atomic model Archives Democritus's Experiment ATOMIC THEORY-1 [DEMOCRITUS] VIDEO Natural Philosophers: Democritus Democritus Ancient Knowledge of Atoms REVEALED 🤫 #shorts #science 1.1 Thought Experiment| Discovery Of Atom| Chapter 1| Class 11| Chemistry| FBISE New Syllabus 2024 History of Chemistry ( Thought Experiment) Atoms in Antiquity: The Vision of Democritus #philosophy COMMENTS Democritus 3. Theory of Perception. Democritus' theory of perception depends on the claim that eidôla or images, thin layers of atoms, are constantly sloughed off from the surfaces of macroscopic bodies and carried through the air. Later atomists cite as evidence for this the gradual erosion of bodies over time. Democritus Democritus (born c. 460 bce —died c. 370) was an ancient Greek philosopher, a central figure in the development of philosophical atomism and of the atomic theory of the universe. Knowledge of Democritus's life is largely limited to untrustworthy tradition. It seems that he was a wealthy citizen of Abdera, in Thrace; that he traveled widely ... Ancient physics: How Democritus predicted the atom The idea of the atom goes as far back as the ancient Greek philosopher Democritus in about 400 B.C.E. This led to his "theory of eidôla" to explain how our minds create the illusion of ... Lesson 1a: Democritus to Dalton The varying properties of matter were explained by the fact that atoms came in a variety of sizes and shapes. Democritus believed that atoms were in constant random motion and their collisions with one another could result in the formation of more sophisticated complexes of atoms. Democritus' atomic theory was not a product of science. Democritus Democritus (/ d ɪ ˈ m ɒ k r ɪ t ə s /, dim-OCK-rit-əs; Greek: Δημόκριτος, Dēmókritos, meaning "chosen of the people"; c. 460 - c. 370 BC) was an Ancient Greek pre-Socratic philosopher from Abdera, primarily remembered today for his formulation of an atomic theory of the universe. [2] Democritus wrote extensively on a wide variety of topics. [3] Who Was Democritus? One such person is Democritus, an ancient Greek philosopher who is viewed by many as being the "father of modern science". This is due to his theory of universe that is made up of tiny ... Democritus' Idea of the Atom One of these philosophers was Democritus (c. 460-370 BCE), often referred to as the "laughing philosopher" because of his emphasis on cheerfulness. He taught that there were substances called atoms and that these atoms made up all material things. The atoms were unchangeable, indestructible, and always existed. Figure 2. The Atomist Philosophers of Ancient Greece: Leucippus, Democritus, and In Democritus's explanation, the atoms in motion in the void were responsible for everything, and no other "cause" was needed. Epicurus introduced "the slight swerve," a new element of causation but with a regrettably unpredictable nature. In addition to the "slight swerve" of the atoms introduced to Democritus's theory, Atom Atom - Development, Theory, Structure: The concept of the atom that Western scientists accepted in broad outline from the 1600s until about 1900 originated with Greek philosophers in the 5th century bce. Their speculation about a hard, indivisible fundamental particle of nature was replaced slowly by a scientific theory supported by experiment and mathematical deduction. It was more than 2,000 ... Atomic model of Democritus of Abdera Democritus claimed that the number of atoms is infinite, they are not created and are eternal, and the qualities of an object depend on the types of atoms that compose it. This theory was later improved and developed by the later Greek philosopher Epicurus (341-270 BC) and the Roman Epicurean poet Lucretius (99-55 BC). Leucippus and Democritus The first proponents of an atomic theory were the Greek philosophers Leucippus and Democritus who proposed the following model in the fifth century B.C. 1. Matter is composed of atoms separated by empty space through which the atoms move. 2. Atoms are solid, homogeneous, indivisible, and unchangeable. Democritus summary Democritus , (born c. 460—died c. 370 bc), Greek philosopher. Though only a few fragments of his work survive, he was apparently the first to describe invisible "atoms" as the basis of all matter. His atoms—indestructible, indivisible, incompressible, uniform, and differing only in size, shape, and motion—anticipated with surprising ... Early Ideas about Matter Because of Aristotle's great influence, Democritus's theory would have to wait almost 2,000 years before being rediscovered. In the 17 th and 18 th centuries CE, several key events helped revive the theory that matter was made of small, ... All matter is composed of indivisible particles called atoms. Bernoulli, Dalton, and others pictured ... Democritus' Idea of the Atom ( Read ) A: The modern kinetic theory of matter is remarkably similar to Democritus' ideas about the motion of atoms. According to this theory, atoms of matter are in constant random motion. This motion is greater in gases than in liquids, and it is greater in liquids than in solids. But even in solids, atoms are constantly vibrating in place. UCSB Science Line In fact, we can even manipulate individual atoms for potentially useful things (more on this later)! But this was not always the case. One of the earliest records we have on the atom came from Democritus, an ancient Greek philosopher (others like Plato and Aristotle had similar trains of thought). Democritus had a thought experiment. essay homework paper phd project resume review speech thesis