180 THE THEORY OF SENSATION'. 



Respecting this system it may be said : — 



First. — That in some classes of sensation, the notion of these 

 phantasms carries with it evident absurdity ; for though we may 

 imagine the phantasm of an object of touch or of vision, who can 

 conceive of the phantasm of a smell or of a sound ? But, secondly, 

 even in the case of sensations of touch and of sight, the existence 

 of these phantasms is utterly destitute of any kind of proof. 



" For these are false, or little else but dreams ; 

 " Conjectures, fancies, built on nothing firm." 



It is a purely gratuitous assumption, and strikingly illustrative of the 

 extraordinary hold which mere conjectures may, for centuries, retain 

 on the human mind. We may say, that for ages the existence of 

 these sensible species was regarded as an indisputable fact, although 

 there was not a tittle of evidence to substantiate it. 



What, then, could have induced philosophers to invent, and so long 

 to retain such a theory ? 



One reason is, the difficulty they felt in accounting for the action 

 of matter on so dissimilar a substance as mind. They, therefore, 

 endeavoured to make matter and mind meet, as it were, half-way, by 

 means of these phantasms, which although material, were so refined, 

 so subtile, so etherial, as to partake, also, in some degree, of the 

 nature of spirit, and, therefore, to be capable of producing on it those 

 impressions which matter in its grosser form was unable to do. 

 But hereby, the line of demarcation which altogether separates the 

 two worlds of mind and matter is taken away; and as matter is 

 spiritualised, so, also, in these phantasms, and the impressions 

 received from them, is spirit materialised. Mind is thus, in fact, 

 regarded as matter, highly etherial, and the distinction between the 

 two worlds is made to be, one not of nature, but degree. 



Another reason which may be adduced to account for the support 

 given to this theory, is found in the notion, that there can be no 

 agency at a distance. In the case of vision, for example, the object 

 supposed to be perceived is at a distance ; it cannot, therefore, act 

 on the eye from which it is absent ; it is, therefore, not the object 

 itself which aflects the organ, but a shadowy film or species trans- 

 mitted from it which produces vision by actual contact. 



The axiom on which this reasoning is based, namely, that the 

 presence of the agent to the object acted upon, is in all cases neces- 

 sary for action, is one, the adoption of which was not restricted to 

 men of ancient days. This will appear from the following quota- 

 tions : — M all ebranche says — "I suppose that everyone will grant 

 that we perceive not the objects that are without us, immediately, 

 and of themselves. We see the sun, the stars, and an infinity of 

 objects without us, and it is not at all likely that the soul sallies out 

 of the body, and, as it were, takes a walk through the heavens to 

 contemplate those objects." " How body acts upon mind, or mind 

 upon body," says Dr. Porterfield, " I know not, but this I am very 

 certain of, that nothing can act, or be acted upon, where it is not ; 

 so that is not the external sun and moon which are in the heavens 



