THE THEORY OF SENSATION. 179 



its organs of sense, are only the unfolding of its latent tendencies. 

 The soul is a monad of the highest order ; all the states in which it 

 exists— its thoughts, and emotions, and determinations being, in like 

 manner, nothing but the developement of the nature with which it was 

 at the first endowed. Yet the changes of the bodily monads do not 

 produce the changes in the spiritual monad. It, indeed, so happens 

 that there is a constant coirespondence between the two ; certain 

 states of the mind which seem to be perfectly suitable to certain 

 states ot the body, do by an extraordinary punctuality, synchronise 

 with them, so that a certain taste is experienced when a certain 

 substance is placed on the tongue ; a sensation of touch or of sight 

 when accordant objects happen to be present to the respective 

 organs ; but this is by virtue of a pre-established harmony, not from 

 any mutual agency between matter and mhid. There is perfect 

 independence, although it has been so ordered that there is exact 

 correspondence, even as, to use a happy illustration, two clocks may 

 keep time together without a second's variation, although there is no 

 connexion between the two. According to this theory, therefore, we 

 should have experienced all our present sensations, even had there 

 been no change in the bodily organs to correspond with them. 



The same difficulty at which Des Cartes and Leibnitz stumbled, 

 gave birth to another theory held by many of the early mystics, but 

 fully developed by Mallebranche, at the close of the seventeenth 

 century. Adopting some of the ancient Platonic notions, he main- 

 tained that God must have had originally in himself the ideas of all 

 things, else He could not have created them ; that the Deity in 

 always present to our souls ; and that on occasion of the impressions 

 made on the body. He reveals His own thoughts to us, so that we 

 perceive not the objects themselves which affect the body, but the 

 ideas of them in the divine mind. This theory was defended on 

 the ground of its simplicity, and of its accordance with the dependent 

 character of man. 



Having thus laid before you, as clearly I have been able to do 

 consistently with brevity, some of the principal theories of other days, 

 I shall now proceed, in the third place, to offer a few remarks in 

 refutation of the errors with which they seem to me to be chargeable. 

 Three sets of difficulties on this subject have perplexed the minds of 

 philosophers. To these three classes those various systems may be 

 refeiTed, and under them I shall arrange the observations I have 

 now to offer. The first difficulty is — how can the influence of the 

 distant object be conveyed to the sensitive organ. The second — 

 how can the impression produced on the organ, be conveyed to the 

 seat of the soul. The third — how can this impression, thus brought 

 into close contact with the soul, originate the sensation. In the 

 journey, therefore, supposed to be made from the external object to 

 the mind there are three different stages. 



To explain the progress made by the cause of the sensation in the 

 first of these stages, Aristotle and his disciples offer us their aid, 

 telling us that films and phantasms fly with lightning speed from the 

 object, and impress the organ of sense. 



