DREAMS, may be defined to he those trains of ideas which occupy the mind, or those imaginary transactions in which it is engaged, during sleep. Dreams constitute some of the most curious phe nomena of the human mind, and have in all ages presented to philosophers a sub ject of most interesting investigation. The theory of dreams embraces two dis tinct classes of phenomena, physical and psychological : the former relate to the question as to how the body is affected in a state of sleep, how the body in that state affects the mind, and how this affection operates to the production of the phe nomena of dreams ; the latter compre hend an inquiry into the laws which reg ulate the train of ideas that occur during sleep, and the mode in which these laws operate, together with an examination of certain psychological appearances pe culiar to that state. To both these classes of phenomena the attention of some of the most distinguished philosophers, both of antiquity and of modern times, has been directed ; and ranch labor and in genuity have been expended in endeavor ing to ascertain the origin and nature of dreams, and to account for the various phenomena by which they are accom panied. Among a multitude of other efficient causes, dreams have been ascrib ed to direct impressions on the organs of sense during sleep,—to the absence of real impressions on the senses,—to a dis ordered state of the digestive organs,— to a less restrained action of the mental faculties,—to the suspension of volition while the powers of sensation continue,— and to the succession and unequal relax ation and cessation of the different senses at the commencement and during the time of sleep. From the remotest period
of antiquity, dreams have also been as cribed to supernatural agency. The rec ords of history, both sacred and profane, abound in instances of dreams which it has been thought impossible to account for on any other hypothesis than that of a supernatural interposition; and, as has been well observed, though there can be no doubt that many dreams which have been considered supernatural, as revealing facts and scientific truths, may now he explained by means within our own knowledge, it can just as little be doubted that many well-authenticated dreams are utterly inexplicable by ordi nary means. This belief in the supernat ural character of dreams is common to every nation in a greater or less degree ; but it prevails more especially in the countries of the East, where, from time immemorial, there has existed a class of persons whose peculiar occupation con sists in the interpretation and explana tion of dreams. Those who wish for com prehensive details on this subject may consult the writings of Aristotle, Lucre tius, Democritus, &c.; and among modern writers, of Locke, Newton, Hartley, Bax ter, Beattie, and Stewart ; and still more recently, those of Abercrombie and Mac nish, which are extremely valuable for the numerous instances of extraordinary dreams with which their theories are il lustrated.