126 SCIENCE AND THE HUMAN MIND 



thought came directly within the ken of natural science. 

 Blaise Pascal (1623-1662) always acknowledged his 

 indebtedness to the writer of the famous Essays; 

 and the whole of the Jansenist colony of Port- Royal, 

 with their rationalist and mystical outlook, in which the 

 Pascal family were deeply involved, displayed much of 

 Montaigne's attitude of mind in their dealings with 

 the orthodox Roman Catholic Church. Pascal was 

 born at Clermont-Ferrand, in the Auvergne, the family 

 having been ennobled during the fifteenth century. 

 As a philosopher, he is best known by his Lettres 

 a un Provincial, attacking the teaching and methods 

 of the Jesuits ; as a mathematician he worked, like 

 Descartes, to generalize the theory of endless particular 

 propositions, and he was the founder of the mathe- 

 matical theory of probability, a study which originated 

 in a discussion concerning the division of stakes in 

 games of chance. His experiments and subsequent 

 treatise on the equilibrium of fluids place him with 

 Stevin and Galileo in developing the science of hydro- 

 dynamics ; while his direction of the famous experi- 

 ment with the barometer on the Puy de Dome, which 

 showed that the height of the mercury column did 

 indeed diminish as the instrument was carried upward, 

 brought home to men's minds the meaning of the 

 discoveries of Galileo and Torricelli. 



But if Galileo and Descartes cleared and prepared 



the ground for Newton, the subject-matter which 



Tycho Brahe his genius moulded into shape had been 



and Kepler. pu t forth ready to his hand, chiefly 



by Tycho Brahe and John Kepler (1571-1630). 



The planetary motions had been measured of old 



