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 proportionably 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 terrours. 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 obser

See the Baron de Torr's Account of the Opium-takers at Constantinople.

vations 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, satisfactory explanation of what some writers have represented as the most mysterious of all the circumstances connected with dreaming; the inaccurate estimate 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* 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 all 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 shew-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.

By means of this supposition of a partial sleep, any apparent exceptions which the history of dreams may afford to the general principles already stated, admit of an easy explanation.

Upon reviewing the foregoing observations, it does not occur to me, that I have in any instance transgressed those rules of philosophizing, which, since the time of Newton, are commonly appealed to, as the tests of sound investigation. For, in the first place, I have not supposed any causes which are not known to exist; and secondly, I have shewn, that the phenomena under our consideration are necessary consequences of the causes to which I have referred them. I have not supposed, that the mind acquires in sleep any new faculty of which we are not conscious while awake; but only (what we know to be a fact) that it retains some of its powers, while the exercise of others is suspended and I have deduced synthetically the known phenomena of dreaming, from the operation of a particular class of our faculties, unconnected by the operation of another. I flatter myself, therefore, that this inquiry will not only throw some light on the state of the mind in sleep, but that it will have a tendency to illustrate the mutual adaption and subserviency which exists among the different parts of our constitution, when we are in complete possession of all the faculties and principles which belong to our nature.*

*See Note (O.)

292

CHAPTER FIFTH.

PART SECOND.

OF THE INFLUENCE OF ASSOCIATION ON THE INTELLECTUAL AND ON THE ACTIVE POWERS.

SECTION 1.

Of the Influence of casual Associations on our speculative Conclusions.

THE Association of Ideas has a tendency to warp our speculative opinions chiefly in the three following ways:

First, by blending together in our apprehensions things which are really distinct in their nature; so as to introduce perplexity and errour into every process of reasoning in which they are involved.

Secondly, by misleading us in those anticipations of the future from the past, which our constitution disposes us to form, and which are the great foundation of our conduct in life.

Thirdly, by connecting in the mind erroneous opinions with truths which irresistibly command our assent, and which we feel to be of importance to human happiness.

A short illustration of these remarks will throw light on the origin of various prejudices; and may, perhaps, suggest some practical hints with respect to the conduct of the understanding.

I. I formerly had occasion to mention several instances of very intimate associations formed between two ideas which have no necessary connection with each other. One of the most remarkable is that which exists in every per