September 23, 1904.] 



SCIENCE. 



391 



a philosopher and a maniac. It was the 

 difference between a live tree and a dead 

 one; between an inert mass and a growing 

 organism. The transition of knowledge 

 from the dead to the living form must, in 

 any complete review of the subject, be 

 looked upon as the really great event of 

 modern times. Before this event the in- 

 tellect was bound down by a scholasticism 

 which regarded knowledge as a roimded 

 whole, the parts of which were written in 

 books and .carried in the minds of men. 

 The student was taught from the begin- 

 ning of his work to look upon authority as 

 the foimdation of his beliefs. The older 

 the authority, the greater the weight it car- 

 ried. So effective was this teaching that 

 it seemed never to have occurred to indi- 

 vidual men that they had every oppor- 

 tunity enjoyed by Aristotle of discovering 

 truth, with, the added advantages of all his 

 knowledge to begin with. "With all the de- 

 velopment of formal logic, that practical 

 logic which could see that the last of a 

 series of authorities, every one of which 

 rested on those which preceded it, could 

 never form a surer foundation for any doc- 

 trine than that supplied by its original pro- 

 pounder. The result of this view of knowl- 

 edge was that, although during the fifteen 

 centuries following the death of the geom- 

 eter of Syracuse, great universities were 

 founded at which generations of professors 

 expounded all the learning of their time, 

 neither professor nor student ever suspect- 

 ed what latent possibilities of good were 

 concealed in the most familiar operations 

 of nature. Every one felt the wind blow, 

 saw water boil and heard the thunder 

 crash, but never thought of investigating 

 the forces here at play. Up to the middle 

 of the fifteenth century the most acute ob- 

 server could scarcely have seen the dawn 

 of a new era. 



In view of this state of things it must 

 be regarded as one of the most remarkable 



facts in evolutionary history that four or 

 five men, whose mental constitution was 

 either typical of the new order of things 

 or who were powerful agents in bringing 

 it about, were all born during the fifteenth 

 century— four of them at least at so nearly 

 the same time as to be contemporaries. 



Leonardo da Vinci, whose artistic genius 

 has charmed succeeding generations, was 

 also the first practical engineer of his time, 

 and the first man after Archimedes to 

 make a substantial advance in developing 

 the laws of motion. That the world was 

 not prepared to make use of his scientific 

 discoveries does not detract from the sig- 

 nificance which must attach to the period 

 of his birth. 



Shortly after him was born the great 

 navigator whose bold spirit was to make 

 known a new world, thus giving to com- 

 mercial enterprise that impetus which was 

 so powerful an agent in bringing about a 

 revolution in the thoughts of men. 



The birth of Leonardo was shortly fol- 

 lowed by that of Copernicus, the first after 

 Aristarchus to demonstrate the true system 

 of the world. In him more than in any 

 of his contemporaries do we see the strug- 

 gle between the old modes of thought and 

 the new. It seems also pathetic and is 

 certainly most suggestive of the general 

 view of knowledge taken at this time that, 

 instead of claiming credit for bringing to 

 light great truths before unknown, he made 

 a labored attempt to show that, after all, 

 there was nothing really new in his system, 

 which he claimed to date from Pythagoras 

 and Philolaus. In this connection it is 

 curious that he makes no mention of Aris- 

 tarchus who, I think, wiU be regarded by 

 conservative historians as his only demon- 

 strated predecessor. To the hold of the 

 older ideas upon his mind we must at- 

 tribute the fact that in constructing his 

 system he took great pains to make as little 

 change as possible in ancient conceptions. 



