David Hartley

“ A reverie differs from imagination only in that the person being more attentive to his own thoughts, and less disturbed by foreign objects, more of his ideas are deducible from association, and fewer from new impressions.
It is to be observed, however, that in all the cases of imagination and reverie, the thoughts depend, in part, upon the then state of body or mind. A pleasurable or painful state of the stomach or brain, joy or grief, will make all the thoughts warp their own way, little or much. ”

“ Fourthly, It is common in dreams for persons to appear to themselves to be transferred from one place to another, by a kind of sailing or flying motion. 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 occasioned. Whatever the reasons be, for which visible images are excited in sleep, like to the objects with which we converse when awake, the same reasons will hold for changes of apparent magnitude and position also ”

“ Thus a person who has taken opium, sees either gay scenes, or ghastly ones, according as the opium excites pleasant or painful vibrations in the stomach. Hence it will follow, that ideas will rise successively in dreams, which have no such connexion as takes place in nature, in actual impressions, nor any such as is deducible from association. And yet, if they rise up quick and vividly one after another, as subjects, predicates, and other associates use to do, they will be affirmed of each other, and appear to hang together. ”

“ At the same time the brain itself is so oppressed, that they have scarce any memory. Persons who read inattentively, i.e. see and speak almost without remembering, also those who labour under such a morbid loss of memory, as that though they see, hear, speak, and act, pro re nata, from moment to moment, yet they forget all immediately, somewhat resemble the persons who walk and talk in sleep.
Fifthly, Dreams consist chiefly of visible imagery. ”

“ But then we cannot have the idea of the vis inertiæ of our own bodies, answering to the impressions in walking; because the nerves of the muscles either do not admit 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 person 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. ”

“ Now this happens, First, Because we have 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: or, if we become quite inattentive to external objects, the reverie does so far put on the nature of a dream, as to appear a reality. Secondly, The trains of visible ideas, which occur in dreams, are far more vivid than common visible ideas ”

“ But if the bodily state be such as favours ideas of anxiety and perplexity, then the inconsistency and apparent impossibility, occurring 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 ”

“ 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 (when the idea of voice comes from that quarter) , or to handle ”