Chap. X!T.] AND PERCEPTION. 175 



Byiicbroiiically ; most of those which are observed succes- 

 sively are frequently observed successively." * But the 

 effects of such repetitions of Sensations, ' associated ' by 

 their occurrence either " precisely at the same instant of 

 time or in the contiguous successive instants," and 

 whether referring to the same object or to different ob- 

 jects, w^ere clearly enunciated nearly a century and a half 

 ago by Hartley in his celebrated ' Doctrine of Associa- 

 tion.'! He then laid down the following important law 

 of Mind: — ''Any S (insect ions, A,B,C, dc, by being asso- 

 ciated with one another a sufficient Number of Times, get 

 such a Poiver over the corresponding Ideas, a, b, c, c&c, 

 that any one of the Sensations A, when impressed alone, 

 shall be able to excite in the Mind b, c, d;c., the Ideas of 

 the rest." Muscular Motions were also shown by 

 Hartley! to exhibit a similar tendency to cohere with 

 Sensations and Ideas, and " the whole doctrine of asso- 

 ciation " was comprised by him in a ' theorem ' to that 

 effect, almost precisely similar to what has been re-affirmed 

 and fully illustrated in our own time, by Alexander Bain, 

 as ' The Law of Contiguity.' 



Hartley, moreover, showed that " Simple Ideas will run 

 into complex ones, by means of Association ; " and on this 

 head James Mill says : — " Ideas, also, which have been so 

 often conjoined that whenever one exists in the mind the 

 other exists along with it, seem to run into one another, 

 to coalesce, as it v/ere, and out of many to form one idea, 

 which idea, however, in reality complex, appears to be no 

 less simple than any one of those of which it is com- 

 pounded. . . . The word 'gold,' for example, or the word 

 *iron,' appears to express as simple an idea as the word 



* James Mill, loc. cit., p. 55. 



t " Oltservations on Man." Sixth Edition, 1834, p. 41. 



J Loc. cit., p. 65. 



