Impressions made upon the senses by external objects return to the mind, as every one knows, in the absence of the objects; and this happens especially with the objects of hearing and of sight; and most so, with the latter. It is, in fact, from the predominance of our conceptions of visible objects, that we have come to apply the wordsidea and image, to the entire class of REPEATED IMPRESSIONS, whencesoever received. The distinctness of our ideas, their permanence, and the power they exert over us, depend upon various circumstances, such as the frequency of the original impression, or its peculiarity, or the vividness of the emotions with which it may happen to have been associated.
Yet these reiterated impressions of external objects or IDEAS, do not always, or usually, return precisely as they entered the mind, but undergo new combinations, infinitely diversified; some of which combinations are formed independently of any act of the mind, while others are the product of its deliberate intention: they also follow each other, in part, in obedience to certain constant principles of association, and, in part, in consequence of the mind's controlling power over them; and it is here, principally, that we find room for that culture of which the faculty is susceptible.
Yet, inasmuch as the elementary ideas of the external world return not precisely as they come, but in modes infinitely diversified, and under new forms of combination, or, as we might say, of configuration, it is manifest, that a small] stock of materialssuch a stock, for example, as may have been accumulated by an infant, during its first two years, will be enough to work up into forms ever and again diversified. Nevertheless, how much soever diversified, the difference between a fortuitous train of ideas furnished by the Conceptive Faculty, and a fixed train supplied by the Memory, is distinctly kept in view; and
