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74 THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 



rhythmic, at one time yielding to a temporary belief in them, at 

 another time criticising them as from an external point of view. 



26. 



These properties of the hypothesis may all be well illus- 

 trated by a brief study of the part played in the development 

 of the science of Chemistry by the concept of the atom. I have 

 already expressed my acceptance of the view that the real 

 significance of the atom in the thought of the Greek school of 

 atomists was its metaphysieal significance its value in con- 

 nection with the solution of the problem of reconciling the 

 Eleatic and Heraclitian views of trie universe. The atom had 

 had a respectably long philosophical history before it appeared 

 in the speculations of Democritus, but there can be no doubt 

 that its origin was the ordinary hard body of well-defined shape 

 and size of everyday experience. In taking this concept from 

 its accustomed context, and using it to "explain" the whole 

 of the structure and behaviour of the world, Democritus 

 neglected those qualitative differences between things which the 

 6/jLoiofjbepeicu of Anaxagoras had preserved ;* but he retained 

 the shape and size and the definite modes of movement which 

 characterise the molar body as we know it, and built up his 

 whole system on the basis of their assumed explanatory value. 

 In this connection it is interesting to note that Bacon, who 

 preferred Democritus to the idealist philosophers of antiquity, 

 was well aware that an atomic theory must necessarily be, an 

 attempt to explain some of the phenomena of matter by means 

 of others. Accordingly he twits Democritus with being " sibi 

 impar et fere contrarius"t not merely for retaining in a 

 theoretical construction which is intended to explain all pro- 

 perties of things, some properties unexplained, but also actually 

 using these retained properties as the means of explanation of 



* See Gompertz (Eng. trans.), Greek Thinkers, i, p. 331. 

 t De Principiis atque Originibus : Works ; ed. Ellis and Spedding, iii, 

 p. 82. 



