On the Scientific Study of Human Nature. 455 



determine the mechanism, modes, and laws of its ac- 

 tion. 



My purpose, on the present occasion, is to show that the 

 doctrine which has prevailed in the past, and still prevails, 

 is doomed to complete inversion ; that the bodily organism 

 which was so long neglected as of no account, is in reality 

 the first and fundamental thing to be considered; and that, 

 in reaching a knowledge of mind and character through the 

 study of the corporeal system, there has been laid the firm 

 foundation of that Science of Human Nature, the comple- 

 tion of which will constitute the next and highest phase in 

 the progress of man. Of course, so vast a subject can re- 

 ceive but scanty justice in the limits of a lecture: the ut- 

 most that I can hope to do will be to present some decisive 

 illustrations of the dependence of mental action upon the 

 bodily system, and to point out certain important results 

 which have been already arrived at by this method of in- 

 quiry. A hasty glance, in the first place, at the several 

 steps by which it has been reached, will help to an under- 

 standing of the present state of knowledge upon the sub- 

 ject. 



The establishment of the modern doctrine, that the 

 brain is the organ of the mind, naturally led to a train of 

 researches into the conditions of the connection. The in- 

 strument of thought, being a part of the living system, is, 

 of course, subject to its laws, and our understanding of its 

 action becomes dependent upon the progress of physio- 

 logical knowledge. Physiology, again, depending upon the 

 various physical sciences, the higher investigation could 

 proceed only with the general advance of inquiry. The 

 discovery of the circulation of the blood laid the founda- 

 tion for the modern science of physiology ; but that dis- 

 covery did not reach its full significance until chemistry 

 had revealed the constitution of matter, and the reciprocal 

 action of its elements : only then was it possible to arrive 



