592 LOGIC OF THE MORAL SCIENCES. 



Secondly. These ideas, or secondary mental states, are excited by our 

 impressions, or by other ideas, according to certain laws which are called 

 Laws of Association. Of these laws the first is, that similar ideas tend to 

 excite one another. The second is, that when two impressions have been 

 frequently experienced (or even thought of) either simultaneously or in im- 

 mediate succession, then whenever one of these impressions, or the idea of 

 it, recurs, it tends to excite the idea of the other. The third law is, that 

 greater intensity in either or both of the impressions is equivalent, in ren- 

 dering them excitable by one another, to a greater frequency of conjunc- 

 tion. These are the laws of ideas, on which I shall not enlarge in this 

 place, but refer the reader to works professedly psychological, in particular 

 to Mr. James Mill's Analysis of the Phenomena of the Human Mind, 

 where the principal laws of association, along with many of their applica- 

 tions, are copiously exemplified, and with a masterly hand.* 



These simple or elementary Laws of Mind have been ascertained by the 

 ordinary methods of experimental inquiry; nor could they have been as- 

 certained 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 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. Revert- 

 ing 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 impressions 

 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 some- 

 times melt and coalesce into one another, and appear not several ideas, but 

 one ; in the same manner as, when the seven prismatic colors are pi'csent- 

 ed 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 colors when they 

 rapidly follow one another generate white, but not that they actually are 

 white ; so it appeal's 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 con- 

 sist of them. Our idea of an orange really consists of the simple ideas of 

 a certain color, a certain form, a certain taste and smell, etc., because we can, 

 by interrogating our consciousness, perceive all these elements in the idea. 



* When this chapter was written, Professor Bain had not yet published even the first part 

 ("The Senses and the Intellect") of his profound Treatise on the Mind. In this the laws 

 of association have been more comprehensively stated and more largely exemplified than by 

 any previous writer ; and the work, having been completed by the publication of " The Emo- 

 tions and the Will," may now be referred to as incomparably the most complete analytical ex- 

 position of the mental phenomena, on the basis of a legitimate Induction, which has yet been 

 produced. More recently still, Mr. Bain has joined with me in appending to a new edition 

 of the "Analysis," notes intended to bring up the analytic science of Mind to its latest im- 

 provements. 



Many striking applications of the laws of association to the explanation of complex mental 

 phenomena are also to be found in Mr. Herbert Spencer's "Principles of Psychology." 



