x VOLITION: LIBERTY AND NECESSITY 219 



sition. A peasant can give no better reason for the stop- 

 ping of any clock or watch, than to say that it does not 

 commonly go right. But an artist easily perceives that 

 the same force in the spring or pendulum has always the 

 same influence on the wheels ; but fails of its usual effect, 

 perhaps by reason of a grain of dust, which puts a stop to 

 the whole movement. From the observation of several 

 parallel instances, philosophers form a maxim, that the 

 connexion between all causes and effects is equally neces- 

 sary, and that its seeming uncertainty in some instances pro- 

 ceeds from the secret opposition of contrary causes." (IV. 

 pp. 101-2.) 



So with regard to human actions: 



" The internal principles and motives may operate in a 

 uniform manner, notwithstanding these seeming irregu- 

 larities ; in the same manner as the winds, rains, clouds, 

 and other variations of the weather are supposed to be 

 governed by steady principles ; though not easily discover- 

 able by human sagacity and inquiry." (IV. p. 103.) 



Meteorology, as a science, was not in existence 

 in Hume's time, or he would have left out the 

 " supposed to be." In practice, again, what dif- 

 ference does any one make between natural and 

 moral evidence? 



" A prisoner who has neither money nor interest, dis- 

 covers the impossibility of his escape, as well, when he con- 

 siders the obstinacy of the gaoler, as the walls and bars 

 with which he is surrounded ; and, in all attempts for his 

 freedom, chooses rather to work upon the stone and iron 

 of the one, than upon the inflexible nature of the other. 

 The same prisoner, when conducted to the scaffold, foresees 

 his death as certainly from the constancy and fidelity of 



