578 SCIENTIFIC THOUGHT. 



meaning and attracted much popular attention in France 

 is. and Belgium through the dominating influence of Lap- 

 lace. He had not only collected in his abstract and 

 very difficult ' Analytical Theory of Probabilities ' all 

 that himself and others had done in this line of research, 

 but he had in a similar manner to that adopted in his 

 ' Celestial Mechanics ' tried to bring the substance of 

 the theory home to the non-mathematical student in 

 his ' Essai Philosophique sur les Probabilite"s.' 



The analytical formulae of probabilities can, he main- 

 tained, " be regarded as the necessary complement of the 

 sciences which are founded on a mass of observations 

 which are subject to error. They are indeed indispens- 

 able for solving a large number of questions in the 

 natural and moral sciences. The regular causes of 

 events are mostly either unknown or too complicated to 

 be submitted to calculation : frequently also their effect 

 is disturbed by accidental and irregular causes, but it 

 always remains impressed on the events produced by 

 all these causes, and it brings about changes which 

 a long series of observations can determine. The 

 analysis of probabilities shows these modifications : it 

 assigns the probability of their causes, and it indicates 

 the means of increasing their probability more and 

 more." 1 Then, referring to the phenomena of the 

 weather, Laplace proceeds : " Moreover, the succession 

 of historical events similarly shows us the constant 

 action of the great moral principles in the midst of 

 the diverse passions and interests which agitate society 

 in every direction. It is remarkable how a science 



1 'Essai Philosophique,' p. 271. 



