pressions. The name, or its idea in the region of the brain corresponding to the ear, are the circumstances most commonly made use of for calling up visible ideas. But there are many ideas, i.e. internal feelings, which have no names, and which yet, by attending our several visible ideas, get this power of introducing them.
Here it is to be observed, that an idea cannot be said to be voluntarily introduced, till it be previously determined by some of its associates. If I desire to introduce a visible idea of any kind, an individuum vagum, and that of a horse offers itself, it was not owing to the command of my will, that it was a horse, and nothing else, but to the connexion which the idea of a horse had with some other idea or impression, which then happened to take place. But if I desire to recollect the features of a person’s face, whom I saw yesterday, I make use of his name, his dress, the place in which I saw him, or some other associated circumstance, for this purpose. And this may be called a voluntary introduction of an idea. However, the introduction of the idea of a horse, in the circumstances just decribed, might be termed voluntary in a different sense, if any person thought fit to denominate it so, on account of the command of the will to introduce some idea. My design here is, only to suggest to the reader the processes generally made use of in these things. It is to be observed farther, that the associated circumstance, which determines what idea shall be called up voluntarily, does, for the most part, raise it. Thus, if a person desire me to call up the idea of a horse, the very sound of the word proceeding from his mouth will do it, for the most part, immediately. If not, I go back, by my memory, to the trace left by the word, and thence to the idea, or to some common associate of both the word and idea, capable of raising the last.
Seventhly, When we have conversed much with the same visible objects, as after having been in a crowd, travelling, &c. for many hours without intermission, we may find the ideas of these objects peculiarly strong, so as to intrude upon our fancies, and interfere with all our other ideas. This may serve to shew, that the permanence of the sensations impressed, mentioned in the third proposition, and which shews itself particularly in visible impressions, as there remarked, is of the nature of an idea. And it coincides remarkably with this, that the ideas should be peculiarly vivid and precise in the same sense, where the permanency of the sensation impressed is most conspicuous.
Eighthly, The ideas of sight and hearing, and the impressions from whence they proceed, have a peculiar connexion with each other. For as words pronounced call up visible ideas, so visible ideas and objects call up the ideas of words, and the actions by which they are pronounced.
Ninthly, The trains of visible ideas are in a particular manner affected by the general states of the brain, as may appear from
