LAWS OF MIND. 437 



a certain number of elementary laws having thus heen 

 obtained, it is a fair subject of scientific inquiry how far those 

 laws can be made to go in explaining the actual phenomena. 

 It is obvious that complex laws of thought and feeling not 

 only may, but must, be generated from these simple laws. 

 And it is to be remarked, that the case is not always one of 

 Composition of Causes : the effect of concurring causes is not 

 always precisely the sum of the effects of those causes when 

 separate, nor even always an effect of the same kind with 

 them. Keverting to the distinction which occupies so pro- 

 minent a place in the theory of induction ; the laws of the 

 phenomena of mind are sometimes analogous to mechanical, 

 but sometimes also to chemical laws. When many impres- 

 sions or ideas are operating in the mind together, there some- 

 times takes place a process, of a similar kind to chemical 

 combination. When impressions have been so often expe- 

 rienced in conjunction, that each of them calls up readily and 

 instantaneously the ideas of the whole group, those ideas 

 sometimes melt and coalesce into one another, and appear not 

 several ideas, but one ; in the same manner as, when the seven 

 prismatic colours are presented to the eye in rapid succession, 

 the sensation produced is that of white. But as in this last 

 case it is correct to say that the seven colours when they 

 rapidly follow one another generate white, but not that they 

 actually are white ; so it appears to me that the Complex Idea, 

 formed by the blending together of several simpler ones, 

 should, when it really appears simple, (that is, when the 

 separate elements are not consciously distinguishable in it,) be 

 said to result from, or be generated by, the simple ideas, not to 

 consist of them. Our idea of an orange really consists of the 

 simple ideas of a certain colour, a certain form, a certain taste 

 and smell, &o., because we can, by interrogating our conscious- 

 ness, perceive all these elements in the idea. But we cannot 

 perceive, in so apparently simple a feeling as our perception of 

 the shape of an object by the eye, all that multitude of ideas 

 derived from other senses, without which it is well ascertained 

 that no such visual perception would ever have had existence ; 

 nor, in our idea of Extension, can we discover those elementary 



