834 



SCIENCE 



IN. S. Vol. XL. No. 1041 



ever, that lie set his contemporaries to think- 

 ing along a new line. Other explanations were 

 offered each of which sought to find a basis for 

 all phenomena in some one material substance. 

 One of these was air. Another was a hypothet- 

 ical substance having properties between those 

 of air and fire. We need not mention more of 

 these. It is sufficient to observe that it was 

 hard to offer a reason why one of them afforded 

 the desired explanation rather than another. 

 One outcome, however, of this discussion 

 among these thinkers is very interesting, 

 namely, the conclusion reached by Anaxagoras 

 that all things have existed in a sort of way 

 from the beginning, but that originally they 

 were in infinitesimally small fragments of 

 themselves, endless in number and inextricably 

 combined throughout the universe but devoid 

 of arrangement. These fragments were the 

 seeds of all things. The gradual adjustments 

 of these among themselves have given rise to 

 all phenomena whatsoever. 



Thus ended the first search among the 

 Greeks for a single material cause of aU things. 

 There followed a long period in which science 

 no longer proposed to itself such an ambitious 

 problem. In modern times each worker has 

 been content to consider a narrow range of 

 phenomena and seek a particular explanation. 

 For a long time we have proceeded in this 

 way with the study of special problems. In 

 recent years we have been brought back in a 

 most surprising manner to face the old prob- 

 lem of the Greeks. In the meantime our 

 chemists and physicists had studied all known 

 substances and had found that they were com- 

 posed of about seventy elements. 



When we had become thoroughly convinced 

 that these elements were separate and distinct, 

 radioactive substances made their appearance 

 in our laboratories and we were compelled to 

 revise our old opinions. Emanations of vari- 

 ous sorts were then eagerly examined and be- 

 fore long it was realized that various of these 

 seventy elements were giving off the same sort 

 of electrons, so that they must certainly have 

 something in common. Moreover, some ele- 

 ments were actually transformed into others. 



In view of these facts one could hardly fail 



to raise the inquiry as to whether all elements 

 are not indeed only different combinations of 

 electrons. The speculative hypotheses of the 

 old Greeks in the earliest period of scientific 

 history thus stand prominently before our 

 physicists in their laboratories to-day. The 

 striking elements of agreement between a 

 theory asserting that all matter is made up of 

 electrons and that of Anaxagoras with its 

 primal fragments of things are very remark- 

 able, to say the least. What is done with this 

 old problem in its new form will certainly exert 

 a marked infiuence on scientific progress. 



Looking from a certain point of view one 

 may say that the great problem of science is 

 to find out just what unities do exist among 

 phenomena. If we can not trace everything 

 to one cause we shall at least seek to find those 

 general laws by means of which the greatest 

 number of phenomena may be explained. This 

 we must do in self-defense; otherwise we 

 should soon be helpless before the enormous 

 volume of science. Only if we grasp the great 

 fundamentals, which include many particulars, 

 shall we be able to continue our progress. 



Economy of energy is one of the great de- 

 mands which will press itself upon our atten- 

 tion with increasing force as the body of sci- 

 ence is enlarged. One way to realize this 

 economy is to make permanent conquests which 

 remain for all time our possession. This is 

 done in the science of mathematics. Other 

 sciences should strive for the same permanence, 

 but be all the time ready to grant that it has 

 not been attained. No law of phenomena 

 should ever be counted so well established as 

 not to be subjected to every further test which 

 ingenuity can devise. Over and over again 

 our fundamental steps of progress have been 

 taken in the most surprising way in fields of 

 thought where everything had apparently been 

 examined with the greatest care. 



The way in which the mathematician has 

 gained economy of energy through permanence 

 of result is instructive. He confines his at- 

 tention within limits so restricted that he may 

 define his terms and ideas with the sharpest 

 precision. In doing this it may be necessary 

 to leave out of account a considerable part of 



