498 LOGIC OF THE MORAL SCIENCES. 



2. All states of mind are immediately caused 

 either by other states of mind, or by states of body. 

 When a state of mind is produced by a state of mind, 

 I call the law concerned in the case, a law of Mind. 

 When a state of mind is produced directly by a state 

 of body, the law is a law of Body, and belongs to phy- 

 sical science. 



With regard to those states of mind which are 

 called Sensations, all are agreed that these have for 

 their immediate antecedents, states of body. Every 

 sensation has for its proximate cause some affection of 

 the portion of our frame called the nervous system ; 

 whether this affection originate in the action of some 

 external object, or in some pathological condition of the 

 nervous organization itself. The laws of this portion 

 of our nature the varieties of our sensations, and the 

 physical conditions on which they proximately depend 

 manifestly fall under the province of Physiology. 



Whether any other portion of our mental states are 

 similarly dependent on physical conditions, is one of 

 those scientific questions respecting human nature 

 which are still in abeyance. It is yet undecided whe- 

 ther our thoughts, emotions, and volitions are gene- 

 rated through the intervention of material mechanism; 

 whether we have organs of thought and of emotion, in 

 the same sense in which we have organs of sensation. 

 Many eminent physiologists hold the affirmative. 

 These contend, that a thought (for example) is as 

 much, the result of nervous agency, as a sensation : 

 that some particular state of our nervous system, in 

 particular of that central portion of it called the brain, 

 invariably precedes, and is presupposed by, every state 

 of our consciousness. ^According to this theory, one 

 state of mind is never really produced by another : all 

 are produced by states of body,"] When one thought 



