510 LOGIC OF THE MORAL SCIENCES. 



mation to be as great as is contended for, it would 

 still be a question how far the cerebral development 

 determined the propensity itself, and how far it only 

 acted by modifying the nature and degree of the sen- 

 sations on which the propensity may be psychologi- 

 cally dependent. And it is certain that, in human 

 beings at least, differences in education and in out- 

 ward circumstances, together with physical differences 

 in the sensations produced in different individuals by 

 the same external or internal cause, are capable of 

 accounting for a far greater portion of character than 

 is supposed even by the most moderate phrenologists. 

 There are, however, many mental facts which do not 

 seem to admit of this mode of explanation. Such, to 

 take the strongest case, are the various instincts of 

 animals, the portion of human nature which corre- 

 sponds to those instincts. No mode has been sug- 

 gested, even by way of hypothesis, in which these 

 can receive any satisfactory, or even plausible, expla- 

 nation from psychological causes alone; and they 

 may probably be found to have as positive, and even 

 perhaps as direct and immediate, a connexion with 

 physical conditions of the brain and nerves, as any of 

 our mere sensations have. 



How much further this remark might be extended, 

 I do not pretend 'to determine. My object is not to 

 establish the doctrines, but to discriminate the true 

 Method, of mental science ; and this, so far as regards 

 the establishment of the general and elementary laws, 

 may be considered to be sufficiently accomplished. 



