V. CHA P. wandering and diffipated habit of thought, which, in the cafe of most perfons, renders their speculations barren of any profit either to themselves or to others. Many theorems, too, have been fuggefted by analogy; many have been investigated from truths formerly known by altering or by generalifing the hypothefis; and many have been obtained by a fpecies of induction. An illustration of these various proceffes of the mind would not only lead to new and curious remarks, but would contribute to diminish that blind admiration of original genius, which is one of the chief obftacles to the improvement of fcience. THE history of natural philosophy, before and after the time of Lord Bacon, affords another very striking proof, how much the powers of invention and discovery may be affifted by the study of method: and in all the fciences, without exception, whoever employs his genius with a regular and habitual fuccefs, plainly fhews, that it is by means of general rules that his inquiries are conducted. Of these rules, there Of these rules, there may be many which the inventor never ftated to himself in words; and, perhaps, he may even be unconscious of the affiftance which he derives from them; but their influence on his genius appears unquestionably from the uniformity with which it proceeds; and in proportion as they can be afcertained by his own fpeculations, or collected by the logician from an examination of his researches, fimilar powers of invention will be placed within the reach of other men, who apply themselves to the fame ftudy. THE following remarks, which a truly philofophical artist has applied to painting, may be extended, with fome trifling "alterations, II alterations, to all the different employments of our intellectual CHA P. powers. "WHAT we now call genius, begins, not where rules, abstractedly taken, end; but where known, vulgar, and "trite rules have no longer any place. It must of neceffity be, "that works of genius, as well as every other effect, as it "must have its cause, muft likewise have its rules; it cannot "be by chance, that excellencies are produced with any con"ftancy, or any certainty, for this is not the nature of chance ; "but the rules by which men of extraordinary parts, and fuch as are called men of genius, work, are either fuch as they "discover by their own peculiar obfervation, or of fuch a nice "texture as not eafily to admit handling or expreffing in "words. "UNSUBSTANTIAL, however, as thefe rules may feem, "and difficult as it may be to convey them in writing, they are ftill feen and felt in the mind of the artist; and he "works from them with as much certainty, as if they were "embodied, as I may fay, upon paper. It is true, these re"fined principles cannot be always made palpable, like the more grofs rules of Art; yet it does not follow, but that the "mind may be put in fuch a train, that it fhall perceive, by a "kind of scientific sense, that propriety, which words can but very feebly fuggeft *." • Difcourfes by Sir Joshua Reynolds. V. CHA P. SECTION V. Application of the Principles flated in the foregoing Sections of this Chapter, to explain the Phenomena of Dreaming. WITH respect to the Phenomena of Dreaming, three dif ferent questions may be proposed. Firft; What is the ftate of the mind in fleep? or, in other words, what faculties then continue to operate, and what faculties are then fufpended? Secondly; how far do our dreams appear to be influenced by our bodily fenfations; and in what refpects do they vary, according to the different conditions of the body in health, and in fickness? Thirdly; what is the change which fleep produces on those parts of the body, with which our mental operations are more immediately connected; and how does this change operate, in diversifying, fo remarkably, the phenomena which our minds then exhibit, from those of which we are confcious in our waking hours? Of these three questions, the first belongs to the Philofophy of the Human Mind; and it is to this question that the following inquiry is almoft entirely confined. The fecond is more particularly interefting to the medical inquirer, and does not properly fall under the plan of this work. The third feems to me to relate to a fubject, which is placed beyond the reach of the human faculties. V. IT will be granted, that, if we could afcertain the ftate of the CHA P. mind in sleep, so as to be able to resolve the various phenomena of dreaming into a fmaller number of more general principles; and ftill more, if we could refolve them into one general fact; we should be advanced a very important ftep in our inquiries upon this fubject; even although we should find it impoffible to fhew, in what manner this change in the ftate of the mind. refults from the change which fleep produces in the state of the body. Such a step would at least gratify, to a certain extent, that difpofition of our nature which prompts us to afcend from particular facts to general laws; and which is the foundation of all our philofophical researches: and, in the prefent inftance, 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 ftate of the mind in fleep, it seems reasonable to expect, that fome light may be obtained, from an examination of the circumftances which accelerate or retard its approach; for when we are disposed to rest, it is natural to imagine, that the ftate of the mind approaches to its ftate in fleep, 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 fleep is accelerated by every circumftance which diminishes or fufpends the exercife of the mental powers; and is retarded by every thing which has a contrary tendency. When we wish for fleep, we naturally endeavour to withhold, as much as poffible, T t V. CHA P. fible, all the active exertions of the mind, by difengaging our attention from every interesting subject of thought. When we are difpofed 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 compofe us to fleep. 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 founds, we fhall find that it confifts wholly of fuch as are fitted to withdraw the attention of the mind from its own thoughts; and are, at the fame time, not sufficiently interesting, to engage its attention to themselves. It is also matter of common obfervation, that children and perfons of little reflexion, who are chiefly occupied about senfible objects, and whofe mental activity is, in a great measure, fufpended, as foon as their perceptive powers are unemployed; find it extremely difficult to continue awake, when they are deprived of their ufual engagements. The fame thing has been remarked of favages, whofe time, like that of the lower animals, is almoft completely divided between fleep and their bodily exertions *. FROM «The exiftence of the Negro flaves in America, appears to participate "more of fenfation than reflection. To this must be ascribed, their difpofition ་ |