re those thoughts which pass through the mind, and those imaginary transactions in which we often fancy ourselves engaged, when in the state of sleep. Of all the subjects upon which the mind of man has speculated, there is perhaps none which has more perplexed philosophers than that of dreaming.

In regard to the immediate cause of dreaming, the opinions of the ancients were very various. Aristotle observes—Every object of sense produces upon the human soul a certain impression, which remains for some time after the object that made it is removed; and which, being afterwards recognised by the perceptive faculty in sleep, gives rise to the varied images which present themselves.

Amongst English writers on this subject, none have written with more acuteness in support of his theory than Baxter. He supposes that our dreams are prompted by separate spirits—an opinion generally entertained by the heathen, and which opinion has given rise, in all ages and in all countries, to endless superstition and imposture—(Essay on the Phenomenon of Dreaming, vol. ii., 3d edit., 1745).

Professor Dugald Stewart, in endeavouring to reduce the phenomenon of dreaming to some established principles, remarks, that in sleep those operations of the mind are suspended which depend on our volition. He then says that, if the suspension of our voluntary operations in sleep be admitted as a fact, there are only two suppositions which can be advanced concerning its cause—the one is, that the power of volition is suspended; the other, that the will loses its influence over those faculties of the mind and those members of the body which, during our waking hours, are subjected to its authority. Now it may be shown that the former is not consistent with fact, whence the latter follows as a necessary consequence. Hence it is inferred that all our mental operations which are independent of our will may continue during sleep; and that the phenomenon of dreaming may, perhaps, be produced by these, diversified in their apparent effects in consequence of the suspension of our voluntary powers. Two obvious consequences follow—1st, That when we are asleep, the succession of our thoughts, in so far as it depends on the association, may be carried on by the operation of the same unknown causes by which it is produced while we are awake; and, 2d, That the order of our thoughts in these two states of our minds must be very different, inasmuch as in the one it depends solely on the laws of association, and in the other on those laws combined with our own voluntary exertions.

If, then, the succession of our thoughts during sleep is regulated by the same general laws of association to which it is subjected while we are awake, and if the circumstances which discriminate dreaming from our waking thoughts are such as must necessarily arise from the suspension of the will, this may account for the inaccurate estimate we form of time when dreaming: the rapidity of thought is such that in the twinkling of an eye a crowd of ideas may pass before us, to which it would take a long discourse to give utterance; and transactions may be conceived which it would require days, or even years, to realize. But in sleep the conceptions of the mind are mistaken for realities, and therefore our estimate of time will be found not according to our experience of the rapidity of thought, but according to our experience of the time requisite for realizing what we conceive.—(Stewart's Elements of the Philosophy of the Human Mind, pp. 328-348.)

There seems a strong analogy between dreaming and insanity. Dr Abercrombie defines the difference between the two states to be, that in the latter the erroneous impression, being permanent, affects the conduct; whereas, in dreaming, no influence on the conduct is produced, because the vision is dissipated on awaking.

Dreams appear to be ordinarily the re-embodiment of thoughts which have before, in some shape or other, occupied the mind. They are broken fragments of our former conceptions revived, and heterogeneously brought together. If they break off from their connecting chain, and become loosely associated, they exhibit oftentimes absurd combinations, but the elements still subsist. If, for instance, any irritation, such as pain, fever, &c., should excite the perceptive organs while the reflective ones are under the influence of sleep, we have a consciousness of objects, colours, or sounds being presented to us, just as if the former organs were actually stimulated by having such impressions communicated to them by the external senses; whilst, in consequence of the repose of the reflecting power, we are unable to rectify the illusion, and conceive that the scenes passing before us, or the sounds that we hear, have a real existence. This want of mutual co-operation between the different faculties of the mind may account for the disjointed character of dreams. This position might be fully substantiated by an appeal to the evidence of fact. Dr Beattie speaks of a man who could be made to dream anything by whispering in his ear. Dr Gregory relates of himself that, having once had occasion to apply a bottle of hot water to his own feet when he retired to bed, he dreamed that he was ascending the side of Mount Etna, and that he found the heat of the ground almost insufferable. Persons who have had a blister applied to their head have been known to dream of being scalped by a party of North American Indians. Sleeping in a smoky room, we may dream of a house or a city being in flames. The smell of a flower applied to the nostrils may call forth the idea of walking in a garden; and the sound of a flute may excite in us the most pleasurable associations.

The only one of our mental powers which is not diminished while dreaming is fancy, or imagination. We often find memory and judgment alternately suspended and exercised. Sometimes we fancy ourselves contemporaneous with persons who have lived ages before; here memory is at work, but judgment is set aside. We dream of carrying on a very connected discourse with a deceased friend, and are not conscious that he is no more; here judgment is awake, but memory suspended.

How God revealed himself by dreams, and raised up persons to interpret them, the Scriptures abundantly testify. That divine dreams, which actually were imparted to God's servants, should be imitated in fictitious representation by ancient and modern writers, was consistent no less with the general objects of superstition and imposture than with those of literature. Hence divine dreams became the constant appendages of the heathen mythology, and accounts, real and fictitious, of communications in vision, were interwoven in every production. Information which was superior to the vulgar philosophy of the time, intimated its discoveries as suggestions imparted by inspiration. If a warning was to be conveyed, what so affecting as the admonition of a departed friend! Such machinery was particularly adapted to works of imagination; and the poems of antiquity, as well as those of modern times, were frequently decorated with its ornaments.