most important acceffion which the philofophy of the human mind has received fince the time of Mr. Locke.

But although Dr. Reid has been at much pains to overturn the old ideal fyftem, he has not ventured to fubftitute 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 speculations. 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 lefs 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 thofe natural feelings of wonder and admiration, at the spectacle of the universe, which are apt to languifh, in confequence of long familiarity. The most profound difcoveries which are placed within the reach of our refearches lead to a confeffion 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

at the fame time, to thofe general and ultimate facts which bound the narrow circle of his knowledge; and which, by evincing to him the operation of powers, whose nature must 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 inquiries; 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 induftry nor ingenuity can pafs. It is a line too, which is marked with fufficient diftinctness; 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 neceffary that we fhould be affured of the existence, in order to lay a foundation for the doctrines of natural theology, it hath not pleafed 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 service to science.

Befide this effect, which is common to all our philofophical pursuits, of impreffing the mind with a fenfe 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,

statement amount?-Merely to this; that the mind is fo formed, that certain impreffions produced on our organs of sense by external objects, are followed by correfpondent fenfations; and that these fenfations, (which have no more refemblance 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 impreflions are made; that all the fteps of this process 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 be. tween the impreffion and the fenfation, may be both arbitrary that it is therefore by no means impoffible, that our sensations may, be merely the occafions on which the correspondent perceptions are excited; and that, at any rate, the confideration of these fenfations, 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 the external objects themfelves, and not any fpecies or images of thefe objects, that the mind perceives; and that, although, by the constitution of our nature, certain fenfations are rendered the conftant antecedents of our perceptions, yet 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 inspired with them, without any concomitant fenfations what

ever.

Thefe remarks are general, and apply to all our various perceptions; and they evidently strike at the

root

root of all the common theories upon the fubject. The laws, however, which regulate these perceptions, are different in the cafe of the different fenfes, and form a very curious object of philofophical 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.

In oppofition to what I have here obferved on the importance of Dr. Reid's fpeculations concerning our perceptive powers, I am fenfible it may be urged, that they amount merely to a negative discovery; and it is poffible, that fome may even be forward to remark, that it was unneceffary to employ fo much labour and ingenuity as he has done, to overthrow an hypothesis of which a plain account would have been a fufficient refutation.-To fuch perfons, I would beg leave to fuggeft, that, although, in confequence of the juster views in pneumatology, which now begin to prevail, (chiefly, I believe, in confequence of Dr. Reid's writings,) the ideal fyftem may appear to many readers unphilofophical and puerile; yet the cafe was very dif ferent when this author entered upon his inquiries: and I may even venture to add, that few pofitive difcoveries, in the whole history of science, can be mentioned, which found a jufter claim to literary reputa tion, than to have detected, fo clearly and unanfwerably, the fallacy of an hypothefis, which has de

fcended

fcended to us from the earliest ages of philofophy; and which, in modern times, has not only ferved to Berkeley and Hume as the bafis of their fceptical fyf tems, but was adopted as an indifputable truth by Locke, by Clarke, and by Newton.

TH

SECTION IV.

Of the Origin of our Knowledge.

HE philofophers who endeavoured to explain the operations of the human mind by the theory of ideas, and who took for granted, that in every exertion of thought there exifts in the mind fome object distinct from the thinking fubftance, were naturally led to inquire whence these ideas derive their origin; in particular, whether they are conveyed to the mind from without by means of the fenfes, or form part of its original furniture? ́

With refpect to this question, the opinions of the ancients were various; but as the influence of these opinions on the prevailing fyftems of the prefent age is not very confiderable, it is not neceffary, for any of the purposes I have in view in this work, to confider them particularly. The moderns, too, have been much divided on the fubject; fome holding with Des Cartes, that the mind is furnished with certain innate ideas; others, with Mr. Locke, that all our ideas' may be traced from fenfation and reflection; and many, (especially among the later metaphyficians in France,) that they may be all traced from fenfation alone.

Of