Historical Relations 145 



was not found in animals. In the pineal gland two clear and 

 distinct ideas produce an absolute mystery. It is there that the 

 mystery of creation is concentrated. 



The Cartesian philosophy was the first complete and coherent 

 system of modern times. It rapidly found adherents and spread 

 in every country and was popular for several generations. In 

 Descartes' native land it won its way even among churchmen. 

 Gradually, however, the numerous physical errors on which it was 

 based were exposed. Towards the end of the century the theory 

 of vortices became quite untenable. It was in fact shown to be 

 inconsistent with astronomical observation, and it did not fit in 

 with either the cosmical system of Newton or the atomic theory 

 which showed signs of revival. As an explanation of cosmic 

 phenomena" it could no longer be held. Moreover, the advance 

 of physiological knowledge exposed the errors of Descartes in the 

 interpretation of the workings of the animal body. Descartes, 

 however, had laid the basis of modern philosophy, and from his 

 time on there has been a continuous chain of thinkers who have 

 claimed to interpret the world by the unaided powers of their own 

 minds. 



The crown of the scientific movement of the seventeenth 

 century is the work of Newton (1642-1727). It happens that, 

 while there is great difficulty in describing or discussing in non- 

 technical language the cosmic theories of Copernicus, Galileo, 

 Kepler, and Descartes, the work of Newton, though no less technical 

 and difficult, can be treated for our particular purpose in very brief 

 fashion. Newton had before him the planetary laws of Kepler. 

 He knew that for every planet the cube of the distance is propor- 

 tional to the square of the time of its revolution, and he sought for 

 some material cause for this. Such a cause he found. 



Law had been traced in the heavens from an early age. The 

 actual laws of planetary and stellar motion had been gradually 

 developed from the simple astronomical theories of the ancients. 

 New laws and new mathematical relationships of the heavenly 

 bodies had been discovered. It had not yet, however, been shown 

 that the natural laws that governed the heavenly bodies were in 

 relation to the laws that govern earthly phenomena. To prove 

 that that relation amounted to identity, to show that the force that 

 causes the stone to fall is the same as that which keeps the planets 

 in their path, was the achievement of Newton, Into the details 



