26 CEREBRAL FORCES. [i. 



powers depends very mucli on the natural perfection or imper- 

 fection of the brain, or on the full or faulty development of the 

 brain at birth, or during growth, &c., of which we have illus- 

 trations in the deformed and compressed heads of many stupid 

 races. 



Note. — The reader must not object to the expression 

 " material idea,^^ because it has been very variously misapplied. 

 By it we understand no hieroglyphical figures of the objects of 

 the conceptions, no impressions stamped on the medullary 

 substance of which one has no conception, and which can only 

 be considered as the fancies of too contemplative philosophers. 

 It is least in our intention, with Bonnet, to analyse the faculties 

 of the soul by means of their altogether unknown qualities. 

 It need only be granted, that the change which takes place 

 in the medullary substance at each conception, is a movement 

 which, since it is unknown, every one may conceive for himself 

 as he pleases; and that we term these movements material ideas , 

 so as to have a short phrase alreadj^ used by writers, instead of a 

 long circumlocution. It will be seen, that throughout the work, 

 we use this expression in no other than this general signification. 

 26. Since every continuous conception in the mind is to be 

 considered at each moment as a prolonged action of the sentient 

 force, and no act of the latter takes place without material ideas 

 in the brain (25), it follows that each continuous conception 

 excites continuous movements in the brain which are usually 

 considered under the term impressions, or representations of the 

 conceptions. The more a conception is developed, or, in other 

 words, the clearer it becomes (Baumgarten^s 'Metaphysics,' 

 § 415), by so much the more fully must the material idea be 

 developed ; if, on the other hand, the conceptions be obscure, 

 there are only imperfect and undeveloped movements in the 

 brain. A more forcible conception requires more vigorous 

 movements (material ideas) in the brain, and more vigorous 

 material ideas develope more forcible conceptions. Since every 

 conception is the origin of a material idea in the brain, and 

 vice versa (25), the more vigorous conceptions are larger con- 

 ceptions so far as they are the origins of material ideas. 

 (Baumgarten's 'Metaphysics' § 379). A large conception 

 contains small conceptions as its constituent parts, and con- 

 sequently it is made up of several, each of which causes a 



