502 LOGIC OF THE MORAL SCIENCES. 



long been ascertained by the ordinary methods of expe- 

 rimental inquiry ; nor could they have been ascertained 

 in any other manner. But a certain number of 

 elementary laws having thus been 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 con- 

 curring 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. Reverting to 

 the distinction which occupies so prominent 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 im- 

 pressions or ideas are operating in the mind together, 

 there sometimes takes place a process, of a similar kind 

 to chemical combination. When impressions have 

 been so often experienced 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 pris^ 

 matic colours are presented to the eye in rapid succes- 

 sion, 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 sepa- 

 rate elements are not consciously distinguishable in it,) 

 be said to result from, or be generated by, the simple 



