xiv.] ON DESCARTES* " DISCOURSE: 1 S3 7 



body as a mere mechanism, and lie looks upon conscious- 

 ness as the peculiar distinction of the " chose pensante" 

 of the "rational soul/' which in man (and in man 

 only, in Descartes' opinion) is superadded to the body. 

 This rational soul he conceived to be lodged in the 

 pineal gland, as in a sort of central oflicc ; and, here, by 

 the intermediation of the animal spirits, it became aware 

 of what was going on in the body, or influenced the 

 operations of the body. Modern physiologists do not 

 ascribe so exalted a function to the little pineal gland, but, 

 in a vague sort of way, they adopt Descartes' principle, 

 and suppose that the soul is lodged in the cortical part 

 of the brain — at least this is commonly regarded as the 

 seat and instrument of consciousness. 



Descartes has clearly stated what he conceived to be 

 the difference between spirit and matter. Matter is sub- 

 stance which has extension, but does not think ; spirit is 

 substance which thinks, but has no extension. It is very 

 hard to form a definite notion of what this phraseology 

 means, when it is taken in connexion with the location 

 of the soul in the pineal gland ; and I can only represent 

 it to myself as signifying that the soul is a mathematical 

 point, having place but not extension, within the limits 

 of the pineal gland. Not only has it place, but it must 

 exert force ; for, according to the hypothesis, it is com- 

 petent, when it wills, to change the course of the animal 

 spirits, which consist of matter in motion. Thus the 

 soul becomes a centre of force. But, at the same time, 

 the distinction between spirit and matter vanishes ; inas- 

 much as -matter, according to a tenable hypothesis, may 

 be nothing but a multitude of centres of force. The 

 case is worse if we adopt the modern vague notion that 

 consciousness is seated in the grey matter of the cere- 

 brum, generally ; for, as the grey matter has extension, 

 that which is lodged in it must also have extension. 



