Page images
PDF
EPUB

SECTION III.

Of Dr. Reid's Speculations on the Subject of Perception.

IT was chiefly in confequence of the fceptical conclufions which Bishop Berkeley and Mr. Hume had deduced from the ancient theories of perception, that Dr. Reid was led to call them in queftion; and he appears to me to have fhewn, in the moft fatisfactory manner, not only that they are perfectly hypothetical, but that the fuppofitions they involve, are abfurd and impoffible. His reafonings, on this part of our conftitution, undoubtedly form the most important acceffion which the philofophy of the hu. man mind has received fince the time of Mr. Locke.

But although Dr. Reid has been at much pains to overturn the old ideal system, he has not ventured to substitute any hypothefis of his own in its place. And, indeed, he was too well acquainted with the limits prescribed to our philofophical inquiries, to think of indulging his curiofity, in fuch unprofitable fpeculations. All, therefore, that he is to be understood as aiming at, in his inquiries concerning our perceptive powers is, to give a precise state of the fact, divefted of all theoretical expreffions; in order to prevent philofophers from impofing on themselves any longer, by words without meaning; and to extort from them an acknowledgment, that, with refpect to the process of nature in perception, they are no less ignorant than the vulgar.

According to this view of Dr. Reid's reafonings, on the fubject of perception, the purpose to which they are fubfervient may appear to fome to be of no very confiderable importance; but the truth is, that one of the most valuable effects of genuine philofophy, is to remind us of the limited powers of the human understanding; and to revive those nat

ural feelings of wonder and admiration, at the fpectacle of the univerfe, which are apt to languish, in confequence of long familiarity. The moft profound discoveries which are placed within the reach of our researches lead to a confeflion of human ignorance; for, while they flatter the pride of man, and increase his power, by enabling him to trace the fimple and beautiful laws by which phyfical events are regulated, they call his attention, at the fame time, to those general and ultimate facts which bound the narrow circle of his knowledge; and which, by evincing to him the operation of powers, whofe nature muft for ever remain unknown, ferve to remind him of the infufficiency of his faculties to penetrate the fecrets of the universe. Wherever we direct our in quiries; whether to the anatomy and phyfiology of animals, to the growth of vegetables, to the chemical attractions and repulfions, or to the motions of the heavenly bodies; we perpetually perceive the effects of powers which cannot belong to matter. To a certain length we are able to proceed; but in every research, we meet with a line, which no industry nor ingenuity can pafs. It is a line too, which is marked with fufficient diftinctnefs; and which no man now thinks of paffing, who has juft views of the nature and object of philofophy. It forms the feparation between that field which falls under the furvey of the phyfical inquirer, and that unknown region, of which, though it was neceflary that we fhould be affured of the exiftence, in order to lay a foundation for the doctrines of natural theology, it hath not pleased the Author of the universe to reveal to us the wonders, in this infant ftate of our being. It was, in fact, chiefly by tracing out this line, that Lord Bacon did fo much fervice to science.

Befides this effect, which is common to all our philofophical purfuits, of impreffing the mind with a fense of that mysterious agency, or efficiency, into

which general laws must be refolved; they have a tendency, in many cafes, to counteract the influence of habit, in weakening thofe emotions of wonder and of curiofity, which the appearances of nature are fo admirably fitted to excite. For this purpose, it is neceffary, either to lead the attention to facts which are calculated to ftrike by their novelty, or to prefent familiar appearances in a new light; and fuch are the obvious effects of philofophical inquiries; fometimes extending our views to objects which are removed from vulgar obfervation; and fometimes correcting our first apprehenfions with refpect to ordinary events. The communication of motion by impulfe, (as I already hinted,) is as unaccountable as any phenomenon we know; and yet, moft men are difpofed to confider it, as a fact which does not refult from will, but from neceffity. To fuch men, it may be useful to direct their attention to the univerfal law of gravitation; which, although not more wonderful in itself, than the common effects of impulse, is more fitted, by its novelty, to awaken their attention, and to excite their curiofity. If the theory of Bofcovich fhould ever be established on a fatisfactory foundation, it would have this tendency in a ftill more remarkable degree, by teaching us that the communication of motion by impulfe, (which we are apt to confider as a neceffary truth,) has no existence whatever; and that every cafe in which it appears to our fenfes to take place, is a phenomenon no lefs inexplicable, than that principle of attraction which binds together the most remote parts of the universe.

If fuch, however, be the effects of our philofophical pursuits when fuccessfully conducted, it must be confeffed that the tendency of imperfect or erroneous theories is widely different. By a fpecious folution of infuperable difficulties, they fo dazzle and bewilder the understanding, as, at once, to prevent

us from advancing, with fteadiness, towards the limit of human knowledge; and from perceiving the existence of a region beyond it, into which philofophy is not permitted to enter. In fuch cafes, it isthe business of genuine fcience to unmask the impofture, and to point out clearly, both to the learned and to the vulgar, what reafon can, and what she cannot, accomplish. This, I apprehend, has been done, with respect to the hiftory of our perceptions, in the most fatisfactory manner, by Dr. Reid.When a perfon little accustomed to metaphyfical fpeculations is told, that, in the cafe of volition, there are certain invifible fluids, propagated from the mind to the organ which is moved; and that, in the cafe of perception, the existence and qualities of the external object are made known to us by means of fpecies, or phantafms, or images, which are present to the mind in the fenforium; he is apt to conclude, that the intercourfe between mind and matter is much less myfterious than he had fuppofed; and that, although thefe expreffions may not convey to him any very diftinct meaning, their import is perfectly understood by philofophers. It is now, I think, pretty generally acknowledged by phyfiologifts, that the influence of the will over the body, is a mystery which has never yet been unfolded; but, fingular as it may appear, Dr. Reid was the first person who had courage to lay completely afide all the common hypothetical language concerning perception, and to exhibit the difficulty in all its magnitude, by a plain statement of the fact. To what then, it may be asked, does this statement amount ?-Merely to this; that the mind is fo formed, that certain impreffions produced on our organs of fenfe by external objects, are followed by correfpondent sensations; and that these sensations,” (which have no more resemblance to the qualities of matter, than the words of a language have to the

things they denote,) are followed by a perception of the existence and qualities of the bodies by which the impreffions are made; that all the fteps of this procefs are equally incomprehenfible; and that, for any thing we can prove to the contrary, the connexion between the fenfation and the perception, as well as that between the impreffion and the fenfation, may be both arbitrary that it is therefore by no means impoffible, that our fenfations may be merely the occafions on which the correspondent perceptions are excited; and that at any rate, the confideration of these sensations, which are attributes of mind, can throw no light on the manner in which we acquire our knowledge of the existence and qualities of body. From this view of the fubject, it follows, that it is external objects themfelves, and not any fpecies or images of these objects, that the mind perceives; and that although, by the conftitution of our nature, certain fenfations are rendered the conftant antecedents of our perceptions, it is juft as difficult to explain how our perceptions are obtained by their means, as it would be, upon the fuppofition, that the mind were all at once infpired with them, without any concomitant fenfations whatever.

These remarks are general, and apply to all our various perceptions; and they evidently ftrike at the root of all the common theories upon the fub. ject. The laws, however, which regulate these perceptions, are different in the cafe of the different fenfes, and form a very curious object of philosophical inquiry.-Thofe, in particular, which regulate the acquired perceptions of fight, lead to fome very interefting and important fpeculations; and, I think, have never yet been explained in a manner completely fatisfactory. To treat of them in detail, does not fall under the plan of this work; but I fhall have occafion to make a few remarks on them, in the chapter on Conception.

« ՆախորդըՇարունակել »