In the preceding chapters we have seen that in order that a thing may be remembered, it must be impressed clearly upon the mind in the first place; and that in order to obtain a clear impression there must be a manifestation of attention. So much for the recording of the impressions. But when we come to recalling, recollecting or remembering the impressions we are brought face to face with another important law of memory--the law of Association. Association plays a part analogous to the indexing and cross-indexing of a book; a library; or another system in which the aim is to readily find something that has been filed away, or contained in some way in a collection of similar things. As Kay says: "In order that what is in the memory may be recalled or brought again before consciousness, it is necessary that it be regarded in connection, or in association with one or more other things or ideas, and as a rule the greater the number of other things with which it is associated the greater the likelihood of its recall. The two processes are involved in every act of memory. We must first impress, and then we must associate. Without a clear impression being formed, that which is recalled will be indistinct and inaccurate; and unless it is associated with something else in the mind, it cannot be recalled. If we may suppose an idea existing in the mind by itself, unconnected with any other idea, its recall would be impossible." All the best authorities recognize and teach the importance of this law of association, in connection with the memory. Abercrombie says: "Next to the effect of attention is the remarkable influence produced upon memory by association." Carpenter says: "The recording power of memory mainly depends upon the degree of attention we give to the idea to be remembered. The reproducing power again altogether depends upon the nature of the associations by which the new idea has been linked on to other ideas which have been previously recorded." Ribot says: "The most fundamental law which regulates psychological phenomena is the law of association. In its comprehensive character it is comparable to the law of attraction in the physical world." Mill says: "That which the law of gravitation is to astronomy; that which the elementary properties of the tissues are to physiology; the law of association of ideas is to psychology." Stewart says: "The connection between memory and the association of ideas is so striking that it has been supposed by some that the whole of the phenomena might be resolved into this principle. The association of ideas connects our various thoughts with each other, so as to present them to the mind in a certain order; but it presupposes the existence of those thoughts in the mind,--in other words it presupposes a faculty of retaining the knowledge which we acquire. On the other hand, it is evident that without the associating principle, the power of retaining our thoughts, and of recognizing them when they