iv DESCARTES' DISCOURSE ON METHOD 189 



pineal gland, 1 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 substance which has extension, but does 

 not think ; spirit is substance which thinks, but 

 has no extension. It is very hard to form a defi- 

 nite notion of what this phraseology means, when 

 it is taken in connection 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 mathe- 

 matical point, having place but not extension, 

 within the limits of the pineal body. Not only 

 has it place, but it must exert force ; for, accord- 

 ing to this hypothesis, it is competent, 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 ; 

 inasmuch as matter, according to a tenable hypo- 

 thesis, 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 cerebrum, generally ; for, 



1 Which, however, as the remains of a Cyclopean eye possessed 

 by some remote ancestor of the Vcrtebrata, has lost none of its 

 interest. [1892.] 



