ATOMISM

(from Greek atoma, things that cannot be cut, or divided), the philosophical doctrine that explains complex phenomena in terms of aggregates of fixed unitary factors, and the scientific view that the material universe is composed of relatively simple and immutable particles too minute to be visible. The various visible forms in nature are thus traced to differences in these particles and their configurations. In order to understand the historical development of atomism and, especially, its relation with modern atomic theory, one must distinguish between atomism in the strict sense and other forms of atomism. Atomism in the strict sense, as propounded by the Greek philosophers Leucippus and Democritus in the 5th century BC, should be regarded as an attempt to reconcile with the data of sensory experience the thesis of Parmenides that matter is unchangeable. Parmenides rejected the possibility of change on rational grounds; change seemed to him to be unintelligible. Democritus agreed with Parmenides on the unintelligibility and impossibility of qualitative change but did not agree with him on the impossibility of quantitative change. This type of change, he maintained, is subject to mathematical reasoning and therefore possible. By the same token, Democritus denied the qualitative multiplicity of visible forms but accepted a multiplicity based on purely quantitative differences. Consequently, the only differences between atoms, according to Democritus, must consist in their size and figure. The infinite variety of observable things could be explained by the different shapes and sizes of the atoms that constituted them and by the different ways in which the atoms were combined. Observable changes were based on a change in combinations of the atoms. During such combinations or separations, however, the atoms themselves remained intrinsically unchanged. Other forms of atomism differed from that conceived by Democritus mainly in two points. First, some atomists, notably Anaxagoras, did not restrict the differences between the atoms to purely quantitative ones but accepted also differences in quality. Secondly, some atomists regarded atoms as divisible, whereas Democritus had regarded them as indivisible. In Greek philosophy there were also transitions between qualitative and quantitative forms of atomism. Plato characterized the atoms of the four elements by different mathematical forms. Examples of qualitative atomism, based upon the doctrine of the four elements, are also found in Indian philosophy. In evaluating the importance of Greek atomism in the light of modern atomic theories, it should be borne in mind that in Greek thought philosophy and science still formed a unity. Greek atomism, then, was inspired as much by the desire to find a solution for the problems of mutability and plurality in nature as by the desire to provide scientific explanations for specific phenomena. While it is true that some of the Greek atomists' ideas can rightly be considered as precursors of later physics, the main importance of the old atomistic doctrine for modern science does not lie in these primitive scientific anticipations. The great achievement of the Greek atomists was that they took a general view of nature as a whole, which made a scientific attitude possible. To this both the quantitative and the qualitative atomism contributed, the former by drawing attention to the mathematical aspects of the problem, the latter by drawing attention to the empirical. While Democritus' influence was eclipsed by that of Aristotle, there were a few adherents of Democritean atomism in later times, notably Epicurus and the Roman poet Lucretius, whose De rerum natura (On the Nature of Things) of about 60 BC constitutes one of the most exhaustive extant accounts of the theory. The general tenets of atomism were revived under the influence of Arabic philosophers during the medieval period and Pierre Gassendi and others in the 17th century. The concept of monads proposed by G.W. Leibniz about 1695 reflects the influence of atomism on other philosophical systems. any doctrine that explains complex phenomena in terms of aggregates of fixed particles or units. This philosophy has found its most successful application in natural science: according to the atomistic view, the material universe is composed of minute particles, which are considered to be relatively simple and immutable and too small to be visible. The multiplicity of visible forms in nature, then, is based upon differences in these particles and in their configurations; hence any observable changes must be reduced to changes in these configurations. Additional reading E. Cantore, Atomic Order: An Introduction to the Philosophy of Microphysics (1969); F. Copleston, A History of Philosophy, 8 vol. (195066); E.J. Dijksterhuis, Die Mechanisierung des Weltbildes (1956; Eng. trans., The Mechanization of the World Picture, 1961), a history of science from antiquity to the 17th century; A.S. Eddington, The Philosophy of Physical Science (1939); K. Lasswitz, Geschichte der Atomistik vom Mittelalter bis Newton, 2 vol. (1890, reprinted 1963), a 19th-century classic; A.G.M. van Melsen, Van atomos naar atoom (1949; Eng. trans., From Atomos to Atom: The History of the Concept Atom, 2nd ed. 1960), including references for the primary sources; L.K. Nash, The Atomic-Molecular Theory (1950), a discussion of the first phase of the chemical atomic theory; E.T. Whittaker, History of the Theories of Aether and Electricity, rev. ed., 2 vol. (195154), only for readers with a solid background in science; L.L. Whyte, Essay on Atomism: From Democritus to 1960 (1961), a brief introduction to the idea of atomism and its history. See also Mrinalkauti Gangopadhyaya, Indian Atomism: History and Sources (1980).