218 PHILOSOPHICAL THOUGHT. 



in fact that sensation is the result of physical vibrations 

 in the nerves, which leave behind them the tendency or 

 habit of vibrating, this being the physical explanation of 

 memory. Hartley took note of only one kind of asso- 

 ciation, viz., association by contiguity, sensations being 

 together, either in space (synchronous) or in time (suc- 

 cessive). James Mill took up the theory of Hartley, but 

 he, like Hartley, confined himself to association in space 

 (synchronism) and association in time (succession), whereas 

 Hume had recognised three forms of association, viz., 

 contiguity in time or space, resemblance, and causality. 



20. James Mill also laid stress upon the fact that, in the 



James Mill's 



mental same way as in chemical compounds, the result or pro- 

 chemistry. 



duct may appear to be simple, and that the elements 

 out of which it is compounded may from various causes 

 become imperceptible. And he as well as Hartley 

 attempted to show how simple mental states may, 

 through the union with others, lead to apparently 

 quite different states. For instance, disinterested love 

 might have been developed out of originally selfish 

 emotion. The principle of association was thus em- 

 ployed to bring unity and simplicity into the chaotic 

 mass of the phenomena of the inner world, and it 

 cannot be denied that the simplicity with which this 

 complicated subject was thus represented did much to 

 recommend the whole scheme. It was further elabor- 

 ated with a very large amount of evidence drawn from 

 original observation, as well as from physiological research, 



21. by Alexander Bain in his two well-known treatises men- 



Alex. Bain. 



tioned above. 1 Bain, however, remedied in addition one 

 1 See p. 27, note 1. 



