It is clear that the visible image of Lincoln's-inn Hall which any one has presented to his senses at any given moment of time cannot have been previously associated with other images and perceptions. Neither is a renewed sensible impression of a particular object the same with or in any manner related to a former recollected impression of the same object except from the resemblance of the one to the other. There can be no doubt then of the connection between my idea or recollection of Lincoln's-inn Hall yesterday, and the associated ideas of the persons whom I saw there, or the things which I heard; the question is, how do I get this idea of yesterday's impression from seeing Lincoln's-inn Hall to-day. The difficulty is not in connecting the links in the chain of previously associated ideas, but in arriving at the first link, in passing from a present sensation to the recollection of a past object. Now this can never be by an act of association, because it is self-evident that the present can never have been previously associated with the past. Every beginning of a series of associations, that is every departure from the continued beaten track of old impressions or ideas remembered in regular succession, therefore implies and must be accounted for from some act of the mind which does not depend on association.
Association is an habitual relation between continuations of the same ideas which act upon one another in a certain manner simply because the original impressions were excited together. Let ABC represent any associated impressions. Let a b c be the ideas left in the mind by these impressions, and then let A M N represent a repetition of A in conjunction with a different set of objects. Now a the idea of A when excited will excite b c or the ideas of B C by association; but A as part of the sensible impression
