I.

pletely established, it would not diminish, in the fmalleft de- CHA P. gree, the value of thofe phyfical inquiries, which have proceeded on the common hypothefis, with refpect to impulfe. The laws which regulate the communication of motion, in the cafe of apparent contact, are the most general facts we obferve among the terreftrial phenomena; and they are, of all phyfical events, thofe which are the moft familiar to us, from our earlieft infancy. It was therefore not only natural but proper, that philofophers fhould begin their phyfical inquiries, with attempting to refer to these, (which are the moft general laws of nature, expofed to the examination of our senses,) the particular appearances they wished to explain. And, if ever the theory of Bofcovich fhould be completely established, it will have no other effect, than to refolve these laws into some principle still more general, without affecting the folidity of the common doctrine, fo far as it goes.

IT

SECTION III.

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

T 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 most fatisfactory manner, not only that they are perfectly hypothetical, but that the fuppofitions they involve, are abfurd

and

I.

CHA P. and impoffible. His reafonings, on this part of our conftitution, undoubtedly form the 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 hypothesis of his own in its place. And, indeed, he was too well acquainted with the limits which Nature has 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 precife ftate of the fact, divested 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 respect to the procefs 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 some 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 natural feelings of wonder and admiration, at the fpectacle of the univerfe, which are apt to languish, in confequence of long familiarity. The most profound discoveries which are placed within the reach of our refearches, instead of laying open to our view the efficient

caufes

powers

I.

causes of natural appearances, lead to a confeffion of human CHA P. 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 physical events are regulated, they call his attention, 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 muft for ever remain unknown, serve to remind him of the insufficiency of his faculties to penetrate the secrets 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 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 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 necessary that we should be affured of the existence, 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 state of our being. It was, in fact, chiefly by tracing. out this line, that Lord Bacon did fo much service to science.

BESIDE this effect, which is common to all our philofophical purfuits, of impreffing the mind with a sense of that

CHA P.

1.

mysterious agency, or efficiency, into which general laws muft
be refolved; they have a tendency, in many cafes, to revive
those emotions of wonder and of curiofity, which the appear-
ances of nature are so admirably fitted to excite; but which
they cease to produce, in consequence of long familiarity. In
order to counteract the influence of habit in weakening these
emotions, it is neceffary either to lead the attention to facts
which are calculated to ftrike by their novelty, or to present to
the mind familiar appearances in a new light: and such are the
necessary and obvious effects of philosophical inquiries; fometimes
extending our views to parts of nature which are removed from
vulgar observation; and fometimes correcting our first ap-
prehenfions with refpect to ordinary events.-The com-
munication of motion by impulfe, (as I already hinted,) is
as unaccountable as any phenomenon we know; and yet,
moft men are disposed 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 universal
law of gravitation; which, although not more wonderful in
itfelf, than the common effects of impulfe, is more fitted, by
its novelty, to awaken their attention, and to excite their curi-
ofity. If the theory of Boscovich should ever be established on
a fatisfactory foundation, it would have this tendency in a still
more remarkable degree, by teaching us that the communica-
tion of motion by impulfe, (which we are apt to confider as a
neceffary truth,) has no existence in nature; and that every
cafe in which it appears to our fenfes to take place, is a phe-
nomenon no less inexplicable, than that principle of attraction
which binds together the most remote parts of the universe.

Iş fuch, however, be the effects of our philofophical purfuits when fuccefsfully 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 steadiness, 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 is the bufinefs of genuine science 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 history of our perceptions, in the most fatisfactory manner, by Dr. Reid.————When a perfon little accustomed to metaphysical 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 exiftence and qualities of the external object are made known to us by means of fpecies, or phantafms, or images, which are prefent to the mind in the fenforium; he is apt to conclude, that the intercourse 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 con

CHAP.

I.