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As all our knowledge of the material world is derived from the information of our fenfes, natural philofophers have, in modern times, wifely abandoned to metaphyficians, all fpeculations concerning the nature of that fubftance of which it is composed; concerning the poffibility or impoffibility of its being created; concerning the efficient caufes of the changes which take place in it; and even concerning the reality of its exiftence, independent of that of percipient beings and have confined themfelves to the humbler province of obferving the phenomena it exhibits, and of ascertaining their general laws. By pursuing this plan fteadily, they have, in the courfe of the two laft centuries, formed a body of science, which not only does honor to the human understanding, but has had a moft important influence on the practical arts of life. This experimenta. philofophy, no one now is in danger of confounding with the metaphysical speculations already mentioned. Of the importance of thefe, as a separate branch of study, it is poffible that fome may think more favorably than others; but they are obviously different in their nature, from the investigations of phyfics; and it is of the utmost confequence to the evidence of this last science, that its principles fhould not be blended with thofe of the former.
A fimilar diftinction takes place among the questions which may be flated relative to the human mind. Whether it be extended or unextended; whether or not it has any relation to place; and (if it has) whether it refides in the brain, or be spread
prove to the contrary, it is possible, that the unknown substance which has the qualities of extension, figure, and colour, may be the same with the unknown substance which has the attributes of feeling, thinking and willing. But besides that this is only an hypothesis, which amounts to nothing more than a mere possibility, even if it were true, it would no more be proper to say of mind, that it is material, than to say of body, that it is spiritual.
over the body, by diffufion; are questions perfectly analogous to those which metaphysicians have started on the fubject of matter. It is unneceffary to inquire at prefent whether or not they admit of anfwer. It is fufficient for my purpose to remark, that they are as widely and obviously different from the view which I propofe to take, of the human mind in the following work, as the reveries of Berkeley concerning the non-existence of the material world, are from the conclufions of Newton and his followers.-It is farther evident, that the metaphysical opinions, which we may happen to have formed concerning the nature either of body or of mind, and the efficient causes by which their phenomena are produced, have no neceffary connexion with our enquiries concerning the laws, according to which these phenomena take place. Whether (for example) the cause of gravitation be material or immaterial, is a point about which two Newtonians may differ, while they agree perfectly in their physical opinions. It is fufficient if both admit the general fact, that bodies tend to approach each other, with a torce varying with their mutual distance, according to a certain law. In like manner in the ftudy of the human mind, the conclufion to which we are led by a careful examination of the phenomena it exhibits, have no neceffary connexion with our opinions concerning its nature and effence. That when two fubjects of thought, for instance, have been repeatedly prefented to the mind in conjunction, the one has a tendency to fuggeft the other, is a fact of which I can no more doubt, than of any thing for which I have the evidence of my fenfes; and it is plainly a fact totally unconnected with any hypothefis concerning the nature of the foul, and which will be as readily admitted by the materialist as by the Berkeleian.
Notwithstanding, however, the reality and importance of this distinction, it has not hitherto been
fufficiently attended to, by the philofophers who have treated of the human mind. Dr. Reid is perhaps the only one who has perceived it clearly, or at leaft who has kept it fteadily in view, in all his inqui ries. In the writings, indeed, of feveral other mod. ern metaphysicians, we meet with a variety of important and well ascertained facts; but in general, thefe facts are blended with fpeculations upon fubjects which are placed beyond the reach of the human faculties. It is this mixture of fact, and of hypothe fis, which has brought the philofophy of mind into fome degree of difcredit; nor will ever its real value be generally acknowledged, till the diftinction I have endeavoured to illuftrate, be understood, and attended to, by those who fpeculate on the fubject. By confining their attention to the fenfible qualities of body, and to the fenfible phenomena it exhibits, we know what discoveries natural philofophers have made and if the labours of Metaphyficians fhall ever be rewarded with fimilar fuccefs, it can only be, by attentive and patient reflection on the fubjects of their own consciousness.
I cannot help taking this opportunity of remarking on the other hand, that if phyfical inquirers fhould think of again employing themselves in fpeculations about the nature of matter, inftead of attempting to ascertain its fenfible properties and laws, (and of late there seems to be fuch a tendency among fome of the followers of Bofcovich,) they will foon involve themselves in an inextricable labyrinth, and the first principles of phyfics will be rendered as myfterious and chimerical, as the pneumatology of the school-men.
The little progrefs which has hitherto been made in the philofophy of mind, will not appear surprising to those who have attended to the hiftory of natural knowledge. It is only fince the time of Lord Bacon, that the study of it has been profecuted with any degree of fuccefs, or that the proper method of con
ducting it has been generally understood. There is even fome reafon for doubting, from the crude fpeculations on medical and chemical fubjects which are daily offered to the public, whether it be yet underftood fo completely as is commonly imagined; and whether a fuller illuftration of the rules of philofophifing, than Bacon or his followers have given, might not be useful, even to physical inquirers.
When we reflect, in this manner, on the fhortness of the period during which natural philofophy has been fuccefsfully cultivated; and at the fame time, confider how open to our examination the laws of matter are, in comparison of thofe which regulate the phenomena of thought, we fhall neither be disposed to wonder, that the philosophy of mind should ftill remain in its infancy, nor be difcouraged in our hopes concerning its future progrefs. The excellent models of this fpecies of inveftigation, which the writings of Dr. Reid exhibit, give us ground to expect that the time is not far diftant when it fhall asfume that rank which it is entitled to hold among the sciences.
It would probably contribute much to accelerate the progrefs of the philofophy of mind, if a distinct explanation were given of its nature and object; and if fome general rules were laid down, with refpect to the proper method of conducting the ftudy of it. To this fubject, however, which is of fufficient extent to furnish matter for a separate work, I cannot attempt to do juftice at prefent; and shall therefore confine myself to the illuftration of a few fundamental principles, which it will be of effential importance for us to keep in view in the following inquirers.
Upon a flight attention to the operations of our own minds, they appear to be fo complicated, and fo infinitely diverfified, that it seems to be impoffible to reduce them to any general laws. In confequence, however, of a more accurate examination, the prof
pect clears up; and the phenomena, which appeared, at first, to be too various for our comprehenfion, are found to be the refuit of a comparatively fmall number of fimple and uncompounded faculties, or of fimple and uncompounded principles of action. Thefe faculties and principles are the general laws of our conftitution, and hold the fame place in the philofophy of mind, that the general laws we inveftigate in phyfics, hold in that branch of science. In both cafes, the laws which nature has established, are to be inveftigated only by an examination of facts; and in both cafes, a knowledge of thefe laws leads to an explanation of an infinite number of phenomena.
In the investigation of phyfical laws, it is well known, that our inquiries must always terminate in fome general fact, of which no account can be given, but that fuch is the conftitution of nature. After we have established, for example, from the aftronomical phenomena, the univerfality of the law of gravitation, it may ftill be afked, whether this law implies the conftant agency of mind; and (upon the fuppofition that it does) whether it be probable that the Deity always operates immediately, or by means of fubordinate inftruments? But these questions, however curious, do not fall under the province of the natural philofopher. It is fufficient for his purpofe, if the univerfality of the fact be admitted.
The cafe is exactly the fame in the philofophy of mind. When we have once afcertained a generai fact; fuch as, the various laws which regulate the affociation of ideas, or the dependence of memory on that effort of the mind which we call Attention; it is all we ought to aim at, in this branch of fcience. If we proceed no farther than facts for which we have the evidence of our own confcioufnefs, our conclufions will be no lefs certain, than thofe in phyfics: but if our curiosity leads us to atC