FROM THALES TO LUCRETIUS, 25 



tion of things by particles of matter ruled in their 

 movements by unvarying laws. This theory he 

 works all round, explaining the processes by which 

 the atoms unite to carry on the birth, growth, and 

 decay of things, the variety of which is due to variety 

 of form of the atoms and to differences in modes 

 of their combination; the combinations being deter- 

 mined by the affinities or properties of the atoms 

 themselves, " since it is absolutely decreed what each 

 thing can and what it cannot do by the conditions of 

 Nature." Change is the law of the universe; what 

 is, will perish, but only to reappear in another form. 

 Death is "the only immortal"; and it is that and 

 what may follow it which are the chief tormentors 

 of men. " This terror of the soul, therefore, and this 

 darkness, must be dispelled, not by the rays of the 

 sun or the bright shafts of day, but by the outward 

 aspect and harmonious plan of Nature." Lucretius 

 explains that the soul, which he places in the centre 

 of the breast, is also formed of very minute atoms of 

 heat, wind, calm air, and a finer essence, the pro- 

 portions of which determine the character of both 

 men and animals. It dies with the body, in support 

 of which statement Lucretius advances seventeen 

 arguments, so determined is he to " deliver those 

 who through fear of death are all their lifetime sub- 

 ject to bondage." 



These themes fill the first three books. In the 

 fourth he grapples with the mental problems of 

 sensation and conception, and explains the origin of 

 3 



