16 THE PRINCIPLES OF SCIENCE. [CHAP. 



results of judicial proceedings have proved of little value, 

 simply because the conditions are far too intricate. As 

 Laplace said, " Tant de passions, d'inte'rets divers et de 

 circonstances compliquent les questions relatives a ces 

 objets, qu'elles sont presque toujours insolubles." Men 

 acting on a jury, or giving evidence before a court, are 

 subject to so many complex influences that no mathema- 

 tical formulas can be framed to express the real conditions. 

 Jurymen or even judges on the bench cannot be regarded 

 as acting independently, with a definite probability in 

 favour of each delivering a- correct judgment. Each man 

 of the jury is more or less influenced by the opinion of the 

 others, and there are subtle effects of character and manner 

 and strength of mind which defy analysis. Even in 

 physical science we can in comparatively few cases apply 

 the theory in a definite manner, because the data required 

 are too complicated and difficult to obtain. But such failures 

 in no way diminish the truth and beauty of the theory 

 itself ; in reality there is no branch of science in which our 

 symbols can cope with the complexity of Nature. As 

 Donkin said, 



" I do not see on what ground it can be doubted that 

 every definite state of belief concerning a proposed hypo- 

 thesis, is in itself capable of being represented by a nume- 

 rical expression, however difficult or impracticable it may 

 be to ascertain its actual value. It would be very difficult 

 to estimate in numbers the vis viva of all the particles of 

 a human body at any instant ; but no one doubts that it is 

 capable of numerical expression." l 



The difficulty, in short, is merely relative to our know- 

 ledge and skill, and is not absolute or inherent in the 

 subject. We must distinguish between what is theo- 

 retically conceivable and what is practicable with our 

 present mental resources. Provided that our aspirations 

 are pointed in a right direction, we must not allow them 

 to be damped by the consideration that they pass beyond 

 what can now be turned to immediate use. In spite of 

 its immense difficulties of application, and the aspersions 

 which have been mistakenly cast upon it, the theory of 

 probabilities, I repeat, is the noblest, as it will in course 



Philosophical Magazine, 4th Series, vol. i. p. 354 



