DREAMS have been described as the imaginations, fancies, or reveries of a sleeping man, and they are said to be de ducible to the three following causes : 1. The impressions and ideas lately receiv ea, and particularly those of the preced ing day. 2. The state of the body, par ticularly the stomach and brain ; and, 3. Association. That dreams are, in part, deducible from the impresssions and ideas of the preceding day, appears from the frequent recurrence of these, especially of the visible ones, in our dreams : in general, ideas that have not affected the mind for some days, recur in dreams only from the second and third causes. That ' fhe state of the body affects our dreams, is evident from the dreams of the sick, and of those who labour under indiges Cons, spasms, and Eatulencies ; and a lit tle observation will shcw that we are car ried on from one thing to another in our dreams partly by association. In proof a what we have advanced, we may ob serve, 1st. That the scenes which pre I , sent themselves in dreams are taken to be real, and we suppose ourselves pre ,- sent, and actuallx seeing and hearing what passes, which is occasioned by there being no other reality to oppose to the ideas which offer themselves ; whereas, in the common fictions of the fancy, while ' we are awake, there is always a set of real external objects striking some of our senses, and precluding a like mistake there. Again, the trains of visible ideas, which occur in dreams, are far more vivid than common visible ideas, an dmay there fore be more easily taken for actual im pressions. 2dly. There is a great wild ness in our dreams ; for the brain, dur ing sleep, is in a state so differentfrom that in which the usual associations were form ed, that they can by ,no means take place during vigilance. The state of the body suggests such ideas, among those that have lately been impressed, as are more suitable to various kinds and degrees of pleasant and painful emotions, excited in the stomach, brain, or other part. Thus a person who has taken opium sees either gay scenes or ghastly ones, according as the opium excites pleasant or painful sen sations in the stomach. Hence, it will follow, that ideas will rise successively in dreams, which have no such connection as take place in nature in actual impres sions, nor any such as is deducible from association; and yet, if they rise up quickly and vividly, one after another, as subjects, predicates, and other associates use to do, they will be affirmed of each other, and appear to bang together. Thus the same person appears in two places at the same time ; two persons, appearing successively in the same place, coalesce into one : a brute is supposed to speak ; any idea, qualification, office, &c. coin ciding in the instant of time with the idea of one's self, or of another person, ad heres immediately, &c. idly. We do not take notice of, or are offended at, these inconsistencies, but pass on from one to another. For the associations, which should lead us thus to take notice, and be offended, are, as it were, asleep ; the bodily causes also hurrying us on to other and new trains successively. But if
the bodily state be such as favours ideas of anxiety and perplexity, then the incon sistency, and apparent impossibility, oc curring in dreams, are apt to give great disturbance and uneasiness. It is to be observed, likewise, that we forget the several parts of our dreams very fast in passing from one to another ; and that this lessens the apparent inconsistencies, and their influences. 4thly. It is common in dreams for persons to appear to them selves to be transferred from one place to another by a kind of sailing or flying mo tion. This arises from the change of the apparent magnitude and position of the images excited in the brain, this change being such as a change of distance and position in ourselves would have occa sioned. Whatever the reasons be, for Which visible images are excited in sleep, like to the objects with which we con verse when awake, the same reasons will hold for changes of apparent magnitude and position also ; and these changes, in fixed objects, being constantly associated with motions in ourselves when awake, will infer these motions when asleep. But then we cannot have the idea of the vi3 inertia of our own bodies answering to the impressions in walking; because the nerves of the muscles either do not ad mit of such miniature vibrations in sleep, or do not transmit ideas to the mind In consequence thereof; whence we appear to sail, fly, or ride. Yet sometimes a per. son seems to walk, and even to strike, just as in other cases he seems to feel the impression of a foreign body on his skin. 5thly. Dreams consist chiefly of visible imagery. This agrees remarkably with the perpetual impressions made upon the optic nerves and corresponding parts of the brain during vigilance, and with the distinctness and vividness of the images impressed. 6thly. It may be observed, that many of the things which are pre. sented in dreams appear to be remem bered by us, or, at least, as familiar to us; and that this may be solved by the readiness with which they start up, and, succeed one another in the fancy. 7thly.
Dreams ought to be soon forgotten, as they are in fact; because the state of the brain suffers great changes in passing from sleep to vigilance. The wildness and incimsistency of our dreams render them still more liable to be forgotten. It is said, that a man may remember his dreams best by continuing in the same posture in which he dreamt, which, if true, would be a remarkable confirma tion of the doctrine of vibrations; since those which take place in the medullary substance of the brain, would be least disturbed and obliterated by this means. 8thly. The dreams which are presented in the first part of the night are, for the most part, much more confused, irregu lar, and difficult to be remembered, than those which we dream towards the morn ing ; and these last are often rational to a considerable degree, and regulated ac cording to the usual course of our associ ations. For the brain begins then to ap proach to the state of vigilance, or that in which the usual associations were form ed and cemented. However, association has some power even in wild and incon sistent dreams.