454 Pleajure from Aftion. [BookX. 



to the body, or ideas affociated with them, is pro- 

 ductive of trouble to the mind, and the contrary *, as 

 will be amply proved in the progrefs of this volume. 



So far is evident from experience. To afcertain the 

 nature and caufe of painful and pleafurable fenfations 

 is an inquiry of fome difficulty. Anatomifts and phy- 

 fiologifts are, I apprehend, very generally agreed in 

 one point ; it will therefore be fufficient to fubjoin the 

 opinion of one. of the moft eminent, efpecially as the 

 fubjedt has been in part invefligated on a former occa- 

 fion f. c All I mall afTume (fays Dr. Monro) is what 

 Is founded on experiments, that fenfation and motion 

 do depend upon the nerves j that fenfations are plea- 

 fant as long as the nerves are only gently affected, with- 

 out any violence offered to them j but as foon as any 

 force goes beyond this, and threatens a folution of 

 union, it creates that uneafy fenfation, pain J.' 



If we examine the courfe of human life, we fhall 

 find almoft the whole of pofitive pleafure to confift in 

 action of fome kind. Sleep will hardly come -under 

 the denomination of pofitive pleafure. It is defired, 

 becaufe it produces a relief from wearinefs, and is a 

 ftate to which our bodies naturally tend when fatigued ; 

 otherwife it is a ftate of infenfibility, and it would be an 

 abufe of language to call it pleafure. Some impreffions 

 are primarily grateful and others difagreeable. That 

 the painful and difagreeable are fuch by an intenfe 

 degree of agitation, which ftrains and prejudices the 

 organs of fenfe, is probable. It is alfo probable, that 

 the agreeable follow the general law of our nature, and 

 are pleafing on account of the gentle yet lively action 



* The expreffion of pain in the countenance is much the fame 

 whether bodily or mental, only differing in the degree, 

 f See book ix. c. 36. 

 See alfo Chefeiden's Anatomy, chap. Nerves. 



2 pr 



