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and reasons about them as such through the whole of his book." In this respect, our English physiologists have far exceeded Diderot himself, who ventured no farther than to affirm, that “every idea “must necessarily resolve itself ultimately into a “sensible representation or picture.” This language of Diderot (a relic of the old ideal system) they have not only rejected with contempt, but they have insisted, that when it was used by the Aristotelians, by Descartes, and by Locke, it was meant by them to be understood only as a figure or metaphor. They have accordingly substituted, instead of it, the supposition, that the immediate objects of thought are either particles of the medullary substance of the brain, or vibrations of these particles, —a supposition which, according to my apprehension of it, is infinitely more repugnant to common sense, than the more enigmatical and oracular language transmitted to us from the dark ages;–while, with all its mechanical apparatus, it does not even touch that difficulty concerning the origin of our knowledge, of which the images and species of the schoolmen sufficiently shew, that these subtile disputants were not altogether unaware. Notwithstanding the celebrity of the names which, in the southern part of Great Britain, have lent their credit to this very bold hypothesis, I cannot bring myself to examine it seriously; recollecting the ridicule which Seneca has incurred, by the gravity of his reply to some of his stoical predecessors, who maintained, that the cardinal virtues are amimals. Wild and incredible as this ancient absurdity may at first appear, it will be found, upon examination, to be fully as reasonable as various tenets which have obtained the suffrages of the learned in our 40wn times. I have only to observe farther at present, with respect to the doctrine of the materiality of our ideas, that it has by no means the merit of so much originality, even in the history of our domestic literature, as was probably believed by some of its late revivers. It appears, from various passages in his works, to have been the decided opinion of Sir Kenelm Digby; and it is enlarged upon and developed, at some length (though evidently without any wish on the part of the author to materialize the mind itself), in a posthumous volume of the celebrated Dr Hooke. The following extract from this last publication, which is now but rarely to be met with, I cannot forbear to introduce here, as an interesting fragment of this sort of physiologico-metaphysical speculation; and I may venture to assert, that the hypothesis which it takes for granted is not inferior, either in point of ingenuity, or in the certainty of the data on which it proceeds, to that of any one of the three noted theorists referred to above. “Memory,” says Hooke, “I conceive to be no“thing else but a repository of ideas, formed partly “from the senses, but chiefly by the soul itself. I “say partly by the senses, because they are, as it “were, the collectors or carriers of the impressions “made by objects from without; delivering them “to the repository, or storehouse, where they are “to be used. This repository I conceive to be “ seated in the brain; and the substance thereof I “conceive to be the material out of which these “ideas are formed, and where they are also pre“served, when formed, being disposed in some re“gular order; which order I conceive to be prin“cipally that according to which they are formed; “ that being first in order that is first formed, and “ that next which is next; and so on continually “by succession, from the time of our birth to the “ time of our death. So that there is, as it were, “a continued chain of ideas coiled up in the repo“sitory of the brain, the first end of which is far“ thest removed from the centre, or seat of the soul, “where the ideas are formed, and the other end is always at the centre, being the last idea form“ed, which is always the moment present when “considered. And, therefore, according as there ... are a greater number of these ideas between the “present sensation or thought in the centre, and “any other, the more is the soul apprehensive of the time interposed.” To those who are acquainted with the strong bent of Hooke's genius towards mechanics, and who recollect that, from his childhood, the art of watchmaking was one of his favourite studies, * it may be amusing to combine, with the foregoing extract, a remark which occurs more than once in the works of Lord Bacon: “When men of confined scien“tific pursuits afterwards betake themselves to phi“losophy, and to general contemplations, they are “apt to wrest and corrupt them with their former “conceits.”—Nor is Hooke the only writer of note, since Bacon’s time, who has exemplified the truth of this maxim. Another illustration of it, still more closely connected with the subject of this

* In the very outset of his work he informs us, that “the word “idea, which has various meanings in metaphysical writers, “may be defined to be a contraction, or motion, or configura“tion of the fibres, which constitute the immediate organ of “sense;”—(Zoonomia, Vol. I. p. 11, 3d edit.) and, in an addendum to the same volume, he compares “the universal prepos. “session, that ideas are immaterial beings, to the stories of ghosts “ and apparitions, which have so long amused the credulous, “ without any foundation in nature.”—(Ibid. p. 513.) I hope it is almost superfluous for me now to repeat, that, according to the view of the subject which I have taken, I do not ascribe to ideas any objective eristence, either as things material, or as things immaterial, and that I use this word merely as synonymous with motion or thought.

Essay, occurs in a profound mathematical work (entitled Harmonics) by Dr Smith of Cambridge. I shall quote the passage I allude to in the author's words, as it contains (independently of its reference to my present purpose) a curious hint towards a physiological theory of the mind, founded on the very same hypothesis which was afterwards adopted by Hartley.—“With a view to some other inqui“ries, I will conclude with the following observa. “tions: That, as almost all sorts of substances are “perpetually subject to very minute vibratory mo“tions, and all our senses and faculties seem chiefly “to depend upon such motions excited in the pro

* See tile A scount of his Life.

“ per organs, either by outward objects, or the “powers of the will, there is reason to expect, that “ the theory of vibrations here given will not prove “useless in promoting the philosophy of other things “besides musical sounds.” " Among modern philosophers, however, I am acquainted with none to whom Bacon's aphorism applies with nearly so great force, as to the ingenious physician whose hypothesis, concerning the materiality of ideas, has led me insensibly into these reflections. The influence of his medical and obstetric occupations on his habits of thinking, may be traced in almost every page of his works, both philosophical and poetical ;-not only in the physiological language in which he uniformly describes our mental operations, but even in his detached theories upon the various incidental questions which he has started. It is sufficient to mention, as instances, his account of the mechanical process by which the human countenance is first moulded into a smile ;and his theory of beautiful forms, deduced from the pleasurable sensations, associated by an infant with the bosom of its nurse. The enthusiastic praise which he bestows on a conjecture of Mr Hume's, that “the world may possibly have been generated “rather than created,” t is perhaps explicable, in part, on the same principle. The propensity which all men have to explain the intellectual phenomena, by analogies borrowed

* See Harmonics, printed at Cambridge in 1749. The preface is dated in 1748. * See Zoonomia, Vol. II, p. 247, 3d edit.

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