HEIDEL. — Ilepl 4>u'o-6WS. 129 



It may be assumed, then, that in the conception of Nature developed 

 by the pre-Socratics all the main senses of the term <£uo-is were com- 

 bined ; that is to say, Nature meant to them not only that out of 

 which things grew or of which, in the last analysis, they are consti- 

 tuted ; this was one of its meanings, but only one, and that not the 

 most important. Certainly it would not be true to say even of the Ioni- 

 ans that they restricted themselves to the question as to the primary 

 substance of the world. Nature (and <£uo-is) meant more than this : it 

 included the law or process of growth exemplified in all things. Aris- 

 totle and Theophrastus suggest that Thales was led to the assumption 

 that water was the primary substance by observations connected with 

 evaporation and precipitation ; be that as it may, it is certain that his 

 successor Anaximander was more interested in the cosmic process of seg- 

 regation than in his colorless Infinite, and thenceforward cosmic pro- 

 cesses and laws occupy the attention of philosophers more and more. 

 The main sense of Nature was, however, the sum of things as consti- 

 tuted by the elements and the cosmic laws and processes. This it was, 

 the Natura Rerum, to the understanding of which the philosopher im- 

 mediately addressed himself; and it was in this sense that the term <f>vo-L<; 

 occurs in the titular phrase Uepl ^vo-ews. Yet, as we have seen, while 

 the inquiry or lo-ropcr) -n-epl ^o-ews concerned the question ' what is it ' 

 (on eVri), the answer at once carried the inquirer to the further ques- 

 tions 'of what is it constituted' and 'how did it come about.' There 

 is nothing startling in this conclusion. It is just what we might have 

 expected, knowing the operations of the human mind. .It is, however, 

 not without a certain interest that we thus discover the ideals of pres- 

 ent-day science informing and impelling the fathers of all science. 



Science, however, merely formulates in the hierarchy of its ideals the 

 interests of the plain man who goes about his daily business with no 

 particular predilection for matters theoretical. The common mind is 

 chiefly concerned with results, neither asking nor greatly caring how 

 they were obtained. As for the underlying causes, material or efficient, 

 which produced the results, they are relatively unimportant, except for 

 the purpose of attaining the same object either actually or by way of 

 ideal construction or verification. Thus every one has heard of the 

 latest invention, say the aeroplane, and accepts it as a fact of interest. 

 Many, though by no means all, know the names of the inventors ; the 

 human interest in personalities of distinction contributes not a little to 

 the attitude of mind which fixes attention upon the author. Even 

 smaller is the number of those who know of what materials the machine 

 is constructed. That is a question of importance chiefly to the practical 

 experimenter. Fewest of all are those who concern themselves about 

 vol. xlv. — 9 



