DREAMS are all those thoughts which pass through the mind, and those imaginary transactions in which we often fancy ourselves engaged when in the state of sleep. Scarcely any part of nature is less open to our observation than the human mind in this state. The dreamer himself cannot well observe the manner in which dreams arise or disappear in his own mind. When he awakes, he cannot recollect the circumstances of his dreams with sufficient accuracy. Were we to watch over him with the most vigilant attention, we could not perceive with certainty what emotions were excited in his mind, or what thoughts passed through it, during his sleep. But though we could ascertain these phenomena, many other difficulties would still remain. What parts of a human being are active, and what dormant, when he dreams? Why does he not always dream while asleep? Or why dreams he at all? Do any circumstances in our constitution, situation, and peculiar character, determine the nature of our dreams?

In treating of this subject, we shall endeavour to lay before our readers such facts as have been ascertained concerning dreaming, together with the most plausible conjectures which have been offered to explain the phenomena of dreams.

In dreaming we are not conscious of being asleep. This is well known from a great variety of circumstances. When awake, we often recollect our dreams; and we remember, on such occasions, that whilst those dreams were passing through our minds, it never occurred to us that we were separated by sleep from the active world. Persons are often observed to act and talk in dreaming as if they were busily engaged in the intercourse of social life.

In dreaming we do not consider ourselves as witnessing or bearing a part in a fictitious scene. We seem not to be in a similar situation with the actors in a dramatic performance, or the spectators before whom they exhibit, but engaged in the business of real life. All the varieties of thought that pass through our minds when awake may also occur in dreams; all the images which imagination presents in the former state may be called up in the latter; the same emotions may be excited, and we are often actuated by equal violence of passion; none of the transactions in which we are capable of engaging whilst awake is impossible in dreams; in short, our range of action and observation is as wide in the one state as in the other; and whilst dreaming, we are not sensible of any distinction between our dreams and the events and transactions in which we are actually concerned in our intercourse with the world.

It is said that all men are not liable to dream. Dr Beattie, in a very pleasing essay on this subject, relates that he knew a gentleman who never dreamed except when his health was in a disordered state; and Locke mentions that a certain person of his acquaintance was almost a stranger to dreaming until the twenty-sixth year of his age, when he began to dream in consequence of having had a fever. These instances, however, are too few, and we have not been able to obtain more; and, besides, it does not appear that those persons had always attended, with the care of a philosopher making an experiment, to the circumstances of their sleep. They might dream, but not recollect their dreams on waking; and they might both dream and recollect their dreams immediately upon awaking, yet afterwards suffer the remembrance of them to slip out of their memory. We do not advance this, therefore, as a certain fact concerning dreaming; we are rather inclined to consider it as a mistake. But though it appears to be by no means certain that any of the human race are throughout the whole of life absolute strangers to dreaming; yet it is well known that all men are not equally liable to dream. The same person dreams more or less at different times; and as one person may be more exposed than another to those circumstances which promote this exercise of fancy, one person may therefore dream more than another. The same diversity will naturally take place in this as in other accidents to which mankind are in general liable.

Though in dreams imagination appears to be free from all restraint, and indulges in the most wanton freaks, yet it is generally agreed that the imaginary transactions of the dreamer bear always some relation to his particular character in the world, his habits of action, and the circumstances of his life. The lover, we are told, dreams of his mistress, the miser of his money; the philosopher reviews his researches in sleep often with the same pain and fatigue as when awake; and even the merchant at times returns to balance his books, and computes the profits of an adventure, when slumbering on his pillow. And not only do the more general circumstances of a person's life influence one's dreams; the passions and habits are nearly the same when asleep as when awake. A person whose habits of life are virtuous, does not in his dreams plunge into a series of crimes; nor are the vicious reformed when they pass into this imaginary world. The choleric man finds himself offended by slight provocations in his dreams as well as in his ordinary intercourse with the world; and a mild temper continues pacific even in sleep.

The character of a person's dreams is influenced by his circumstances when awake in a still more unaccountable manner. Certain dreams usually arise in the mind after a person has been in certain situations. Dr Beattie relates that once, after riding thirty miles in a high wind, he passed a part of the succeeding night in dreams beyond description terrible. The state of a person's health, and the manner in which the vital functions are carried on, have a considerable influence in determining the character of dreams. After too full a meal, or after eating of an unusual sort of food, a person is very apt to be harassed with uncomfortable dreams.

In dreaming, the mind for the most part carries on no intercourse through the senses with surrounding objects. Touch a person gently who is asleep, and he feels not the impression. You may awake him by a smart blow; but when the stroke is not sufficiently violent to awake him, he remains insensible of it. We speak softly beside a person asleep, without fearing that he will overhear us. His eyelids are shut; and even though light should fall upon the eyeball, yet still his powers of vision are not awakened to active exertion, unless the light be strong enough to rouse him from sleep. He is insensible both to sweet and to disagreeable smells. It is not easy to try whether his organs of taste retain their activity, without awakening him; yet from analogy it may be presumed that these too are inactive. With respect to the circumstances here enumerated, it is indifferent whether a person be dreaming or buried in deep sleep.

Yet there is one remarkable fact concerning dreaming, which may appear contradictory of what has been here asserted. In dreams we are liable not only to speak aloud in consequence of the suggestions of imagination, but even to get up and walk about, and engage in little enterprises, without awaking. Now, as we are in this instance so active, it seems that we cannot be then insensible of the presence of surrounding objects. The sleep-walker is really sensible in a certain degree of the presence of the objects around him; but he does not attend to them with all their circumstances, nor do they excite in him the same sensations as if he were awake. He feels no terror on the brink of a precipice, and in consequence of being free from fear, he is also without danger in such a situation, unless suddenly awaked. This is one of the most inexplicable phenomena of dreaming.

There is also another fact not quite consonant with what has been above mentioned. It is said that in sleep a person will continue to hear the noise of a cataract in the neighbourhood, or regular strokes with a hammer, or any similar sound sufficiently loud, and continued uninterruptedly from before the time of his falling asleep. We know not whether he awakes on the sudden cessation of the noise; but the fact is asserted, on apparently sufficient evidence, and it is curious. Even when awake, if very deeply intent on any piece of study, or closely occupied in business, the sound of a clock striking in the neighbourhood, or the beating of a drum, will escape us unnoticed; and it is therefore the more surprising that we should thus continue sensible to sounds when asleep.

Not only do a person's general character, habits of life, and state of health, influence his dreams; but those concerns in which he has been most deeply interested during the preceding day, and the views which have arisen most frequently to his imagination, very often afford the subjects of his dreams. When we look forward with anxious expectation towards any future event, we are likely to dream either of the disappointment or the gratification of our wishes. If we have been engaged throughout the day either in business or amusements which we have found exceedingly agreeable, or in a way in which we have been extremely unhappy, either our happiness or our misery is likely to be renewed in our dreams.

Though dreams have been regarded amongst almost all nations of the world, at some periods of their history, as prophetic of future events, yet it does not appear that this popular opinion has ever been established on any good grounds. Christianity, indeed, teaches us to believe that the Supreme Being may, and actually does, operate on our minds, and influence at times the determinations of our will, without making us sensible of the restraint to which we are thus subjected; and, in the same manner, no doubt, the suggestions which arise to us in dreams may be produced. The imaginary transactions in which we are then engaged may be such as are actually to occupy us in life; the strange and seemingly incoherent appearances which are presented to the mind's eye in our dreams, may allude to some events which are to befall ourselves or others. It is therefore by no means impossible, or inconsistent with the general analogy of nature, that dreams should have a respect to futurity. We have no reason to regard the dreams related in the Holy Scriptures as not inspired by Heaven, nor to laugh at the idea of a prophetic dream as absurd or ridiculous. At the same time, a mind which, during its waking hours, is filled with anxious thoughts and presentiments of the future, may reproduce these forebodings in its dreams, when the imagination acts over again the scenes of the past day, embellished and diversified with its own peculiar colouring; and as, from the mere law of probabilities, the actual result must sometimes correspond with the anticipative vision; and the dream be realised by the event, the apparent prophetic intimation is thus as much the consequence of natural causes and of the ordinary workings of the mind, as any of the phenomena which it exhibits. To accident alone is to be ascribed that correspondence which, among the uneducated or the unreflecting portion of mankind, passes for divination by means of supernatural agency; and though the cases where it occurs are necessarily few, compared with those in which the event falsifies the prognostications of the dreamer, yet being calculated to make a much stronger impression on the mind, they are remembered, whilst the others are forgotten; and hence the exception is, by a natural transition, converted into the rule.

Yet it would be too much to allow to dreams all that importance which has been ascribed to them by the priesthood among heathens, or by the vulgar among ourselves. We know how easily ignorance imposes on itself, and what arts imposture adopts to impose upon others. We cannot trace any certain connection between our dreams and those events to which the simplicity of the vulgar pretends that they refer. And we cannot, therefore, if disposed to confine our belief to certain or probable truths, join with the vulgar in believing them really referrible to futurity.

It appears that the brutes are also capable of dreaming. The dog is often observed to start suddenly up in his sleep, in a manner which cannot be accounted for in any other way than by supposing that he is roused by some impulse received in a dream. The same thing is observable of others of the inferior animals. That they should dream, is not an idea inconsistent with what we know of their economy and manners in general. We may therefore consider it as a pretty certain truth, that many, if not all, of the lower species are liable to dream, as well as human beings.

It appears, then, that in dreaming we are not conscious of being asleep; that to a person dreaming, his dreams seem realities; that although it be uncertain whether mankind are all liable to dream, yet it is well known that they are not all equally liable to dream; that the nature of a person's dreams depends in some measure on his habits of action, and on the circumstances of his life; that the state of the health, too, and the manner in which the vital functions are carried on, have a powerful influence in determining the character of a person's dreams; that in sleep and in dreaming, the senses are either absolutely inactive, or nearly so; that such concerns as we have been very deeply interested in during the preceding day, are very likely to return upon our minds in dreams in the hours of rest; that dreams may be rendered prophetic of future events; that therefore, wherever we have such evidence of their having been prophetic as we would accept on any other occasion, we cannot reasonably reject the fact on account of its absurdity; that, however, they do not appear to have been actually such, in those instances in which the superstition of nations ignorant of true religion has represented them as referring to futurity, nor in those instances in which they are viewed in the same light by the vulgar among ourselves; and, lastly, that dreaming is not a phenomenon peculiar to human nature, but common to mankind with the brutes.

We scarcely know of any other facts that have been fully ascertained concerning dreaming. But we are by no means sufficiently acquainted with this important phenomenon in the history of mind. We cannot tell by what laws of our constitution we are thus liable to be so frequently engaged in imaginary transactions, nor what are the particular means by which the delusion is accomplished. The delusion is indeed remarkably strong. One will sometimes have a book presented to him in a dream, and fancy that he reads; and actually enter into the nature of the imaginary composition before him, and even remember, after he awakes, what he knows that he only fancied himself reading. Can this be delusion? If delusion, how or for what purposes is it produced? The mind, it would appear, does not, in sleep, become inactive like the body, or at least is not always inactive while we are asleep. When we do not dream, the mind must either be inactive, or the connection between the mind and the body. Dreams must be considered as in some manner suspended; and, when we dream, the mind, though it probably acts in concert with the body, yet does not act in the same manner as when we are awake. It seems to be clouded or bewildered, in consequence of being deprived for a time of the service of the senses. Imagination becomes more active and more capricious; and all the other powers, especially judgment and memory, get disordered and irregular in their operation.

Various theories have been proposed to explain what appears here most inexplicable. Mr Baxter, in his treatise on the immateriality of the human soul, endeavours to prove that dreams are produced by the agency of some spiritual beings, who either amuse or employ themselves seriously in engaging mankind in all those imaginary transactions with which they are employed in dreaming. This theory, however, is far from being plausible. It leads us entirely beyond the limits of our knowledge; it requires us to believe without evidence; it is unsupported by any analogy; and it creates difficulties still more inexplicable than those which it has been proposed to remove. Until it be made to appear that our dreams cannot possibly be produced without the interference of spiritual agents, possessing such influence over our minds as to deceive us with fancied joys, and to involve us in imaginary afflictions, we cannot reasonably refer them to such a cause. Besides, from the facts which have been stated as well known concerning dreams, it appears that their nature depends both on the state of the human body and on that of the mind. But were they owing to the agency of other spiritual beings, how could they be influenced by the state of the body with reference to health or sickness, fasting or repletion? They must be a curious set of spiritual beings who depend in such a manner on the state of our corporeal frame. Better not to allow them existence at all, than to place them in such a dependence.

Wolffius, and after him Formey, have supposed that dreams never arise in the mind, except in consequence of some of the organs of sensation having been previously excited. Either the ear or the eye, or the organs of touching, tasting, or smelling, communicate information in a tacit and secret manner, and thus partly rouse its faculties from the lethargy in which they are buried in sleep, and engage them in a series of confused and imperfect exertions. But what passes in dreams is so very different from all that we do when awake, that it is impossible for the dreamer himself to distinguish whether his powers of sensation perform any part on the occasion. It is not necessary that imagination should be always excited by immediate sensation. Fancy, even when we are awake, often wanders from the present scene. Absence of mind is incident to the studious; the poet and the mathematician many times forget where they are. We cannot discover from any thing that a person in dreaming displays to the observation of others, that his organs of sensation take part in the imaginary transactions in which he is employed. In those instances, indeed, in which persons asleep are said to hear sounds, the sounds which they hear are said also to influence in some manner the nature of their dreams. But such instances are singular. Since then it appears that the person who dreams is himself incapable of distinguishing, either during his dreams, or by recollection when awake, whether any new impressions are communicated to him in that state by his organs of sensation; that even by watching over him, and comparing our observations of his circumstances and emotions in his dreams with what he recollects of them after awaking, we cannot, except in one or two singular instances, ascertain this fact; and that the mind is not wholly incapable of acting while the organs of sensation are at rest, and on many occasions refuses to listen to the information which they convey; we may without hesitation conclude that the theory of Wolffius and Formey has been too hastily and incautiously advanced.

Other physiologists tell us that the mind when we dream is in a state of delirium. Sleep, they say, is attended with what is called a collapse of the brain; during which either the whole or a part of the nerves of which it consists are in a state in which they cannot carry on the usual intercourse between the mind and the organs of sensation. When the whole of the brain is in this state, we become entirely unconscious of existence, and the mind sinks into inactivity; when only a part of the brain is collapsed, as they term it, we are then neither asleep nor awake, but in a sort of delirium between the two. This theory, like that last mentioned, supposes the mind incapable of acting without the help of sensation; it supposes that we know the nature of a state of which we cannot ascertain the phenomena; and it contradicts a well-known fact, in representing dreams as confused images of things around us, instead of fanciful combinations of things not existing together in nature or in human life. For these reasons it must be held as wholly inadmissible.

Of all the writers who have treated of this subject, however, Mr Dugald Stewart is perhaps the only one who, by concentrating the lights of a sound philosophy on the results of refined and accurate observation, has been enabled to classify the phenomena of dreams, and to introduce the order of science into a department of speculative inquiry where fancy had previously reigned paramount. "Dreams," says Mr Addison, "look like the relaxations and amusements of the soul when she is disencumbered of her machine; her sports and recreations when she has laid her charge asleep. The soul is clogged and retarded in her operations when she acts in conjunction with a companion that is so heavy and unwieldy in its motions; but in dreams she converses with numberless beings of her own creation, and is transported into ten thousand scenes of her own raising. She is herself the theatre, the actor, and the beholder." This description, which is not more beautiful than true, will serve to convey some idea of the difficulties of disentangling mental operations necessarily so complex, and of keeping steadily in view the threefold character or agency which the mind exhibits in dreaming; and as the only approximation which has yet been made towards the accomplishment of so interesting an object is contained in Mr Stewart's section on the application of the principles and laws of association to explain the phenomena of dreaming (Elements of the Philosophy of the Human Mind, vol. i. p. 327, sixth edition, Lond. 1818, 8vo), we conceive that we cannot do better than subjoin this exquisite specimen of philosophical acuteness and discrimination, in the author's own beautiful language.

"With respect to the phenomena of dreaming," says Mr Stewart, "three different questions may be proposed. First, what is the state of the mind in sleep? or, in other words, what faculties then continue to operate, and what faculties are then suspended? Secondly, how far do our dreams appear to be influenced by our bodily sensations; and in what respects do they vary, according to the different conditions of the body in health and in sickness? Thirdly, what is the change which sleep produces on those parts of the body with which our mental operations are more immediately connected; and how does this change operate, in diversifying, so remarkably, the phenomena which our minds then exhibit, from those of which we are conscious in our waking hours? Of these three questions, the first belongs to the philosophy of the human mind; and it is to this question that the following inquiry is almost entirely confined. The second is more particu- It will be granted, that, if we could ascertain the state of the mind in sleep, so as to be able to resolve the various phenomena of dreaming into a smaller number of general principles; and still more, if we could resolve them into one general fact; we should be advanced a very important step in our inquiries upon this subject; even although we should find it impossible to show in what manner this change in the state of the mind results from the change which sleep produces in the state of the body. Such a step would at least gratify, to a certain extent, that disposition of our nature which prompts us to ascend from particular facts to general laws, and which is the foundation of all our philosophical researches; and, in the present instance, I am inclined to think that it carries us as far as our imperfect faculties enable us to proceed.

In conducting this inquiry with respect to the state of the mind in sleep, it seems reasonable to expect, that some light may be obtained from an examination of the circumstances which accelerate or retard its approach; for when we are disposed to rest, it is natural to imagine that the state of the mind approaches to its state in sleep more nearly than when we feel ourselves alive and active, and capable of applying all our various faculties to their proper purposes.

In general, it may be remarked, that the approach of sleep is accelerated by every circumstance which diminishes or suspends the exercise of the mental powers, and is retarded by every thing which has a contrary tendency. When we wish for sleep, we naturally endeavour to withhold, as much as possible, all the active exertions of the mind, by disengaging our attention from every interesting subject of thought. When we are disposed to keep awake, we naturally fix our attention on some subject which is calculated to afford employment to our intellectual powers, or to rouse and exercise the active principles of our nature.

It is well known that there is a particular class of sounds which compose us to sleep. The hum of bees, the murmur of a fountain, the reading of an uninteresting discourse, have this tendency in a remarkable degree. If we examine this class of sounds, we shall find that it consists wholly of such as are fitted to withdraw the attention of the mind from its own thoughts; and are, at the same time, not sufficiently interesting to engage its attention to themselves.

It is also matter of common observation, that children, and persons of little reflexion, who are chiefly occupied about sensible objects, and whose mental activity is in a great measure suspended as soon as their perceptive powers are unemployed, find it extremely difficult to continue awake when they are deprived of their usual engagements. The same thing has been remarked of savages, whose time, like that of the lower animals, is almost completely divided between sleep and their bodily exertions.

From a consideration of these facts, it seems reasonable to conclude, that in sleep those operations of the mind are suspended which depend on our volition; for if it be certain, that before we fall asleep, we must withhold, as much as we are able, the exercise of all our different powers, it is scarcely to be imagined that, as soon as sleep commences, these powers should again begin to be exerted. The more probable conclusion is, that when we are desirous to procure sleep, we bring both mind and body as nearly as we can into that state in which they are to continue after sleep commences. The difference, therefore, between the state of mind when we are inviting sleep, and when we are actually asleep, is this, that in the former case, although its active exertions be suspended, we can renew them if we please. In the other case, the will loses its influence over all our powers both of mind and body, in consequence of some physical alteration in the system, which we shall never probably be able to explain.

In order to illustrate this conclusion a little farther, it may be proper to remark, that if the suspension of our voluntary operations in sleep be admitted as a fact, there are only two suppositions which can be formed 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. If it can be shown then that the former supposition is not agreeable to fact, the truth of the latter seems to follow as a necessary consequence.

1. That the power of volition is not suspended during sleep, appears from the efforts which we are conscious of making while in that situation. We dream, for example, that we are in danger, and we attempt to call out for assistance. The attempt indeed is in general unsuccessful, and the sounds which we emit are feeble and indistinct; but this only confirms, or rather is a necessary consequence of the supposition that, in sleep, the connexion between the will and our voluntary operations is disturbed or interrupted. The continuance of the power of volition is demonstrated by the effort, however ineffectual.

In like manner, in the course of an alarming dream, we are sometimes conscious of making an exertion to save ourselves, by flight, from an apprehended danger; but in spite of all our efforts we continue in bed. In such cases we commonly dream that we are attempting to escape, and are prevented by some external obstacle; but the fact seems to be, that the body is at that time not subject to the will. During the disturbed rest which we sometimes have when the body is indisposed, the mind appears to retain some power over it; but as, even in these cases, the motions which are made consist rather of a general agitation of the whole system, than of the regular exertion of a particular member of it, with a view to produce a certain effect, it is reasonable to conclude that, in perfectly sound sleep, the mind, although it retains the power of volition, retains no influence whatever over the bodily organs.

In that particular condition of the system which is known by the name of incubus, we are conscious of a total want of power over the body; and I believe the common opinion is, that it is this want of power which distinguishes the incubus from all the other modifications of sleep. But the more probable supposition seems to be, that every species of sleep is accompanied with a suspension of the faculty of voluntary motion; and that the incubus has nothing peculiar in it but this, that the uneasy sensations which are produced by the accidental posture of the body, and which we find it impossible to remove by our own efforts, render us distinctly conscious of our incapacity to move. One thing is certain, that the instant of our waking, and of our recovering the command of our bodily organs, is one and the same.

2. The same conclusion is confirmed by a different view of the subject. It is probable, as was already observed, that when we are anxious to procure sleep, the state into which we naturally bring the mind approaches to its state after sleep commences. Now it is manifest that the means which nature directs us to employ on such occasions, is not to suspend the power of volition, but to suspend the exertion of those powers whose exercise depends on volition. If it were necessary that volition should be suspended before we fall asleep, it would be impossible for us by our own efforts to hasten the moment of rest. The very supposition of such efforts is absurd, for it implies a continued will to suspend the acts of the will.

According to the foregoing doctrine with respect to the state of the mind in sleep, the effect which is produced on our mental operations is strikingly analogous to that which is produced on our bodily powers. From the observations which have been already made, it is manifest that in sleep the body is, in a very inconsiderable degree, if at all, subject to our command. The vital and involuntary motions, however, suffer no interruption, but go on as when we are awake, in consequence of the operation of some cause unknown to us. In like manner, it would appear that those operations of the mind which depend on our volition are suspended, while certain other operations are at least occasionally carried on. This analogy naturally suggests the idea that all our mental operations which are independent of our will may continue during sleep, and that the phenomena of dreaming may perhaps be produced by these, diversified in their apparent effects, in consequence of the suspension of our voluntary powers.

If the appearances which the mind exhibits during sleep are found to be explicable on this general principle, it will possess all the evidence which the nature of the subject admits of.

It was formerly shown that the train of thought in the mind does not depend immediately on our will, but is regulated by certain general laws of association. At the same time it appeared, that among the various subjects which thus spontaneously present themselves to our notice, we have the power of singling out any one that we choose to consider, and of making it a particular object of attention; and that by doing so we not only can stop the train that would otherwise have succeeded, but frequently can divert the current of our thoughts into a new channel. It also appeared that we have a power (which may be much improved by exercise) of recalling past occurrences to the memory by a voluntary effort of recollection.

The indirect influence which the mind thus possesses over the train of its thoughts is so great, that during the whole time we are awake, excepting in those cases in which we fall into what is called a reverie, and suffer our thoughts to follow their natural course, the order of their succession is always regulated more or less by the will. The will, indeed, in regulating the train of thought, can operate only (as I already showed) by availing itself of the established laws of association; but still it has the power of rendering this train very different from what it would have been if these laws had taken place without its interference.

From these principles, combined with the general fact which I have endeavoured to establish with respect to the state of the mind in sleep, two obvious consequences follow. First, that when we are in this situation, the succession of our thoughts, so far as it depends on the laws of association, may be carried on by the operation of the same unknown causes by which it is produced while we are awake; and, secondly, that the order of our thoughts in these two states of the mind must be very different; inasmuch as in the one it depends solely on the laws of association; and in the other, on these laws combined with our own voluntary exertions.

In order to ascertain how far these conclusions are agreeable to truth, it is necessary to compare them with the known phenomena of dreaming; for which purpose I shall endeavour to show, first, that the succession of our thoughts in sleep is regulated by the same general laws of association to which it is subjected while we are awake; and, secondly, that the circumstances which discriminate dreaming from our waking thoughts are such as must necessarily arise from the suspension of the influence of the will.

1. That the succession of our thoughts in sleep is regulated by the same general laws of association which influence the mind while we are awake, appears from the following considerations.

Our dreams are frequently suggested to us by bodily sensations; and with these it is well known, from what we experience while awake, that particular ideas are frequently very strongly associated. I have been told by a friend, that having occasion, in consequence of an indisposition, to apply a bottle of hot water to his feet when he went to bed, he dreamed that he was making a journey to the top of Mount Etna, and that he found the heat of the ground almost insupportable. Another person, having a blister applied to his head, dreamed that he was scalped by a party of Indians. I believe every one who is in the habit of dreaming will recollect instances, in his own case, of a similar nature.

2. Our dreams are influenced by the prevailing temper of the mind, and vary in their complexion according as our habitual disposition at the time inclines us to cheerfulness or to melancholy. Not that this observation holds without exception; but it holds so generally, as must convince us that the state of our spirits has some effect on our dreams as well as on our waking thoughts. Indeed, in the latter case, no less than in the former, this effect may be counteracted or modified by various other circumstances.

After having made a narrow escape from any alarming danger, we are apt to awake in the course of our sleep with startings, imagining that we are drowning, or on the brink of a precipice. A severe misfortune, which has affected the mind deeply, influences our dreams in a similar way, and suggests to us a variety of adventures analogous in some measure to that event from which our distress arises. Such, according to Virgil, were the dreams of the forsaken Dido.

3. Our dreams are influenced by our prevailing habits of association while awake.

In a former part of this work I considered the extent of that power which the mind may acquire over the train of its thoughts; and I observed that those intellectual diversities among men, which we commonly refer to peculiarities of genius, are at least in a great measure resolvable into differences in their habits of association. One man possesses a rich and beautiful fancy, which is at all times obedient to his will. Another possesses a quickness of recollection, which enables him at a moment's warning to bring together all the results of his past experience, and of his past reflections, which can be of use for illustrating any proposed subject. A third can without effort collect his attention to the most abstract questions in philosophy; can perceive at a glance the shortest and the most effectual process for arriving at the truth; and can banish from his mind every extraneous idea which fancy or casual association may suggest to distract his thoughts or to mislead his judgment. A fourth unites all these powers in a capacity of perceiving truth with an almost intuitive rapidity, and in an eloquence which enables him to command at pleasure whatever his memory and fancy can supply to illustrate and to adorn it. The occasional exercise which such men make of their powers may undoubtedly be said, in one sense, to be unpremeditated or unstudied; but they all indicate previous habits of meditation or study, as unquestionably as the dexterity of the expert accountant, or the rapid execution of the professional musician.

From what has been said, it is evident that a train of thought which in one man would require a painful effort of study, may in another be almost spontaneous; nor is it to be doubted that the reveries of studious men, even when they allow, as much as they can, their thoughts to follow their own course, are more or less connected together by those principles of association which their favourite pursuits tend more particularly to strengthen.

"The influence of the same habits may be traced distinctly in sleep. There are probably few mathematicians who have not dreamed of an interesting problem, and who have not even fancied that they were prosecuting the investigation of it with much success. They whose ambition leads them to the study of eloquence are frequently conscious, during sleep, of a renewal of their daily occupations; and sometimes feel themselves possessed of a fluency of speech which they never experienced before. The poet in his dreams is transported into Elysium, and leaves the vulgar and unsatisfactory enjoyments of humanity, to dwell in those regions of enchantment and rapture which have been created by the divine imaginations of Virgil and of Tasso.

"As a farther proof that the succession of our thoughts in dreaming is influenced by our prevailing habits of association, it may be remarked, that the scenes and occurrences which most frequently present themselves to the mind while we are asleep are the scenes and occurrences of childhood and early youth. The facility of association is then much greater than in more advanced years; and although during the day the memory of the events thus associated may be banished by the objects and pursuits which press upon our senses, it retains a more permanent hold of the mind than any of our subsequent acquisitions; and, like the knowledge which we possess of our mother tongue, is, as it were, interwoven and incorporated with all its most essential habits. Accordingly, in old men, whose thoughts are in a great measure disengaged from the world, the transactions of their middle age, which once seemed so important, are often obliterated; while the mind dwells, as in a dream, on the sports and the companions of their infancy.

"I shall only observe farther, on this head, that in our dreams, as well as when awake, we occasionally make use of words as an instrument of thought. Such dreams, however, do not affect the mind with such emotions of pleasure and of pain, as those in which the imagination is occupied with particular objects of sense. The effect of philosophical studies, in habituating the mind to the almost constant employment of this instrument; and, of consequence, its effect in weakening the imagination, was formerly remarked. If I am not mistaken, the influence of these circumstances may also be traced in the history of our dreams, which in youth commonly involve in a much greater degree the exercise of imagination, and affect the mind with much more powerful emotions, than when we begin to employ our maturer faculties in more general and abstract speculations.

"II. From these different observations we are authorized to conclude, that the same laws of association which regulate the train of our thoughts while we are awake, continue to operate during sleep. I now proceed to consider how far the circumstances which discriminate dreaming from our waking thoughts, correspond with those which might be expected to result from the suspension of the influence of the will.

"1. If the influence of the will be suspended during sleep, all our voluntary operations, such as recollection, reasoning, &c. must also be suspended.

"That this really is the case, the extravagance and inconsistency of our dreams are sufficient proofs. We frequently confound together times and places the most remote from each other; and, in the course of the same dream, conceive the same person as existing in different parts of the world. Sometimes we imagine ourselves conversing with a dead friend, without remembering the circumstance of his death, although perhaps it happened but a few days before, and affected us deeply. All this proves clearly that the subjects which then occupy our thoughts are such as present themselves to the mind spontaneously, and that we have no power of employing our reason in comparing together the different parts of our dreams, or even of exerting an act of recollection, in order to ascertain how far they are consistent and possible.

"The processes of reasoning in which we sometimes fancy ourselves to be engaged during sleep, furnish no exception to the foregoing observation; for although every process, the first time we form it, implies volition, and, in particular, implies a recollection of the premises till we arrive at the conclusion, yet when a number of truths have been often presented to us as necessarily connected with each other, this series may afterwards pass through the mind according to the laws of association, without any more activity on our part than in those trains of thought which are the most loose and incoherent. Nor is this mere theory. I may venture to appeal to the consciousness of every man accustomed to dream, whether his reasonings during sleep do not seem to be carried on without any exertion of his will, and with a degree of facility of which he was never conscious while awake. Mr Addison, in one of his Spectators, has made this observation; and his testimony, in the present instance, is of the greatest weight, that he had no particular theory on the subject to support. 'There is not,' says he, 'a more painful action of the mind than invention, yet in dreams it works with that ease and activity that we are not sensible when the faculty is employed. For instance, I believe every one, some time or other, dreams that he is reading papers, books, or letters; in which case the invention prompts so readily, that the mind is imposed on, and mistakes its own suggestions for the composition of another.' No.487.

"2. If the influence of the will during sleep be suspended, the mind will remain as passive, while its thoughts change from one subject to another, as it does during our waking hours, while different perceptible objects are presented to our senses.

"Of this passive state of the mind in our dreams it is unnecessary to multiply proofs, as it has always been considered as one of the most extraordinary circumstances with which they are accompanied. If our dreams as well as our waking thoughts were subject to the will, is it not natural to conclude, that in the one case, as well as in the other, we would endeavour to banish, as much as we could, every idea which had a tendency to disturb us, and detain those only which we found to be agreeable? So far, however, is this power over our thoughts from being exercised, that we are frequently oppressed, in spite of all our efforts to the contrary, with dreams which affect us with the most painful emotions. And, indeed, it is matter of vulgar remark, that our dreams are, in every case, involuntary on our part, and that they appear to be obtruded on us by some external cause. This fact appeared so unaccountable to the late Mr Baxter, that it gave rise to his very whimsical theory, in which he ascribes dreams to the immediate influence of separate spirits on the mind.

"3. If the influence of the will be suspended during sleep, the conceptions which we then form of sensible objects will be attended with a belief of their real existence, as much as the perception of the same objects is while we are awake.

"In treating of the power of Conception, I formerly observed, that our belief of the separate and independent existence of the objects of our perceptions, is the result of experience; which teaches us, that these perceptions do not depend on our will. If I open my eyes, I cannot prevent myself from seeing the prospect before me. The case is different with respect to our conceptions. While they occupy the mind, to the exclusion of every thing else, I endeavoured to shew that they are always accompanied with belief; but as we can banish them from the mind, during our waking hours, at pleasure, and as the momentary belief which they produce is continually checked by the surrounding objects of our perceptions, we learn to consider them as fictions of our own creation, and, excepting in some accidental cases, pay no regard to them in the conduct of life. If the doctrine, however, formerly stated with respect to conception be just, and if, at the same time, it be allowed that sleep suspends the influence of the will over the train of our thoughts, we should naturally be led to expect, that the same belief which accompanies perception while we are awake, should accompany the conceptions which occur to us in our dreams. It is scarcely necessary for me to remark, how strikingly this conclusion coincides with acknowledged facts.

"May it not be considered as some confirmation of the foregoing doctrine, that when opium fails in producing complete sleep, it commonly produces one of the effects of sleep, by suspending the activity of the mind, and throwing it into a reverie; and that while we are in this state, our conceptions frequently affect us nearly in the same manner as if the objects conceived were present to our senses?

"Another circumstance with respect to our conceptions during sleep deserves our notice. As the subjects which we then think upon occupy the mind exclusively, and as the attention is not diverted by the objects of our external senses, our conceptions must be proportionally lively and steady. Every person knows how faint the conception is which we form of any thing with our eyes open, in comparison of what we can form with our eyes shut; and that in proportion as we can suspend the exercise of all our other senses, the liveliness of our conception increases. To this cause is to be ascribed, in part, the effect which the dread of spirits in the dark has on some persons who are fully convinced in speculation that their apprehensions are groundless; and to this also is owing the effect of any accidental perception in giving them a momentary relief from their terrors. Hence the remedy which nature points out to us when we find ourselves overpowered by imagination. If every thing around us be silent, we endeavour to create a noise by speaking aloud or beating with our feet; that is, we strive to divert the attention from the subjects of our imagination by presenting an object to our powers of perception. The conclusion which I draw from these observations is, that as there is no state of the body in which our perceptive powers are so totally unemployed as in sleep, it is natural to think that the objects which we conceive or imagine must then make an impression on the mind beyond comparison greater than any thing of which we can have experience while awake.

"From these principles may be derived a simple, and, I think, a satisfactory explanation of what some writers have represented as the most mysterious of all the circumstances connected with dreaming; the inaccurate estimates we are apt to form of time while we are thus employed—an inaccuracy which sometimes extends so far as to give to a single instant the appearance of hours, or perhaps of days. A sudden noise, for example, suggests a dream connected with that perception; and the moment afterwards this noise has the effect of awaking us; and yet during that momentary interval a long series of circumstances has passed before the imagination. The story quoted by Mr Addison (Spectator, No. 94) from the Turkish Tales, of the miracle wrought by a Mahometan doctor to convince an infidel sultan, is in such cases nearly verified.

"The facts I allude to at present are generally explained by supposing that, in our dreams, the rapidity of thought is greater than while we are awake; but there is no necessity for having recourse to such a supposition. The rapidity of thought is at times such, that in the twinkling of an eye, a crowd of ideas may pass before us to which it would require a long discourse to give utterance; and transactions may be conceived which it would require days to realize. But in sleep the conceptions of the mind are mistaken for realities; and therefore our estimates of time will be formed, not according to our experience of the rapidity of thought, but according to our experience of the time requisite for realizing what we conceive. Something perfectly analogous to this may be remarked in the perceptions we obtain by the sense of sight. When I look into a show-box, where the deception is imperfect, I see only a set of paltry daubings of a few inches diameter; but if the representation be executed with so much skill as to convey to me the idea of a distant prospect, every object before me swells in its dimensions, in proportion to the extent of space which I conceive it to occupy; and what seemed before to be shut up within the limits of a small wooden frame, is magnified, in my apprehension, to an immense landscape of woods, rivers, and mountains.

"The phenomena which we have hitherto explained take place when sleep seems to be complete; that is, when the mind loses its influence over all those powers whose exercise depends on its will. There are, however, many cases in which sleep seems to be partial; that is, when the mind loses its influence over some powers, and retains it over others. In the case of the somnambuli, it retains its power over the limbs, but it possesses no influence over its own thoughts, and scarcely any over the body, excepting those particular members of it which are employed in walking. In madness, the power of the will over the body remains undiminished, while its influence in regulating the train of thought is in a great measure suspended, either in consequence of a particular idea, which engrosses the attention, to the exclusion of every thing else, and which we find it impossible to banish by our efforts, or in consequence of our thoughts succeeding each other with such rapidity that we are unable to stop the train. In both of these kinds of madness, it is worthy of remark, that the conceptions or imaginations of the mind becoming independent of our will, they are apt to be mistaken for actual perceptions, and to affect us in the same manner."

Some very beautiful fables have been written both by ancients and moderns in the form of dreams. The Somnium Scipionis, for instance, is perhaps one of the finest of Cicero's compositions. He who shall carefully peruse this piece, with Macrobius's commentary thereupon, will undoubtedly acquire a considerable knowledge of ancient philosophy. In the periodical publications which early diffused so much elegant and useful knowledge throughout Britain, the Tatlers, Spectators, Guardians, and the like, we find a number of excellent dreams. Addison excelled in this line of writing; his Vision of Mirza is a masterpiece of its kind. But the public are now less partial to this species of composition than they formerly were; writings purely imaginative, having ceased to be relished, are no longer produced.