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Continuation of the subject—Indistinctness of the line drawn by Reid, as well as by Descartes and Locke, between the Primary and the Secondary qualities of Matter.—Distinction between the Primary qualities of Matter and its Mathematical Affections. .*

I have yet another criticism to offer on Dr Reid’s reasonings with respect to perception ;—a criticism not founded upon any flaw in his argument, but upon his imattention, in enumerating the primary qualities of matter, to a very essential distinction among the particulars comprehended in his list; by stating which distinction, he might, in my opinion, have rendered his conclusions much more clear and satisfactory. Into this oversight Dr Reid was very naturally led by the common arrangement of his immediate predecessors; most of whom, since the time of Locke, have classed together, under the general title of primary qualities, hardness, softness, roughness, smoothness, &c. with eatension, figure, and motion. In this classification he has invariably followed them, both in his Inquiry into the Human Mind, and in his Essays on the Intellectual Powers; a circumstance the more remarkable, that he has incidentally stated, in different parts of his works, some very important considerations, which scem to point out obviously the necessity of a more strictly logical arrangement. After observing, on one occasion, that “hardness “and softness, roughness and smoothness, figure “and motion, do all suppose extension, and cannot “ be conceived without it ;” he adds, that “ he “thinks it must, on the other hand, be allowed, “that if we had never felt anything hard or soft, “rough or smooth, figured or moved, we should “never have had a conception of extension: so that, “as there is good ground to believe that the notion “of extension could not be prior to that of other “primary qualities; so it is certain that it could “not be posterior to the notion of any of them, be“ing necessarily implied in them all.” " In another passage, the same author remarks, that “though the notion of space seems not to enter “at first into the mind, until it is introduced by “the proper objects of sense; yet, being once in“troduced, it remains in our conception and belief, “ though the objects which introduced it be removed. “We see no absurdity in supposing a body to be “annihilated ; but the space that contained it re

* According to Locke, the primary qualities of matter are solidity, extension, figure, motion, or rest, and number. (Book ii. chap. viii. § 9.) In the theory of Berkeley, the word solidity is employed as synonymous with hardness and resistance. (Berkeley's Works, p. 133. Vol. I. Dublin edition of 1784.) Following these guides, Reid has been led to comprehend, in his enumeration (very inadvertently in my opinion), the heterogeneous qualities specified in the text.

“mains; and to suppose that annihilated, seems to “be absurd.”f

* Inquiry, chap. v. sect. 5. + Essays on the Int. Powers, p. 262, 4to edition.

Among the various inconveniences resulting from this indistinct enumeration of primary qualities, one of the greatest has been, the plausibility which it has lent to the reasonings of Berkeley and of Hume, against the existence of an external world. Solidity and eatension being confounded together by both, under one common denomination, it seemed to be a fair inference, that whatever can be shewn to be true of the one, must hold no less when applied to the other. That their conclusions, even with respect to solidity, have been pushed a great deal too far, I have already endeavoured to shew ; the resistance opposed to our compressing force, manifestly implying the existence of something external, and altogether independent of our perceptions :—but still there is a wide difference between the notion of independent existence, and that ascribed to eatension or space, which, as Dr Reid observes, carries along with it an irresistible conviction, that its existence is eternal and necessary, equally incapable of being created or annihilated. The same remark may be applied to the system of Dr Hutton, who plainly considered extension and hardness as qualities of the same order; and who, in consequence of this, has been led to blend (without any advantage whatever to the main object of his work) the metaphysics of Berkeley with the physics of Boscovich, so as to cast an additional obscurity over the systems of both. It is this circumstance that will be found, on examination, to be the principal stumbling-block in the Berkeleian theory, and which distinguishes it from that of the Hindoos, and from all others com

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monly classed along with it by metaphysicians; that it involves the annihilation of space as an external existence; thereby unhinging completely the natural conceptions of the mind with respect to a truth, about which, of all within the reach of our faculties, we seem to be the most completely ascertained ; and which, accordingly, was selected by Newton and Clarke as the ground-work of their argument for the necessary existence of God."

* This species of sophistry, founded on an indistinctness of classification, occurs frequently in Berkeley's writings. It is thus that, by confounding primary and secondary qualities under one common name, he attempts to extend to both, the conclusions of Descartes and Locke with respect to the latter. “To what purpose is it,” he asks, “to dilate on that which may “be demonstrated with the utmost evidence in a line or two, to “any one that is capable of the least reflection ? It is but looking “into your own thoughts, and so trying whether you can con“ceive it possible for a sound, or figure, or motion, or colour, to “exist without the mind, or unperceived. This easy trial may “make you see, that what you contend for is a downright con“tradiction; insomuch, that I am content to put the whole on “this issue, if you can but conceive it possible for one ertended “moveable substance, or, in general, for any one idea, or anything “like an idea, to exist otherwise than in a mind perceiving it, I “shall readily give up the cause.”—Principles of Human Knowledge, section xxii. o

The confusion of thought which runs through the foregoing passage was early remarked by Baxter, in his Inquiry into the Nature of the Human Soul. In the first sentence, he observes, that “figure and motion are nicely shuffled in with colour and “sound, though they are qualities of a different kind; and, in “ the last, that extended moveable substance is supposed to be “a species of idea;”—“in which case,” he adds, “Dr Berke“ley is very safe in his argument.” (Vol. II, p. 276. 3d edit.) * This phrase I borrow from some of the elementary treatises of Natural Philosophy.

I am always unwilling to attempt innovations in language; but I flatter myself it will not be considered as a rash or superfluous one, after the remarks now made, if I distinguish Extension and Figure by the title of the mathematical affections of matter; * restricting the phrase primary qualities to hardness and softness, roughness and smoothness, and other properties of the same description. The line which I would draw between primary and secondary qualities is this; that the former necessarily involve the notion of eatension, and consequently of eaternality or outness; t whereas the latter are only conceived as the unknown causes of known sensations; and, when first apprehended by the mind, do not imply the existence of anything locally distinct from the subjects of its own consciousness. But these topics I must content myself with merely hinting at on the present occasion. †

t The word outness, which has been of late revived by some of Kant's admirers in this country, was long ago used by Berkeley in his Principles of Human Knowledge (sect. xliii.); and, at a still earlier period of his life, in his Essay towards a new Theory of Vision (sect. xlvi.) I mention this, as I have more than once heard the term spoken of as a fortunate innovation.

f For Locke's distinction between Primary and Secondary qualities, see his Essay, Book ii. chap. iii. § 9. Of its logical accuracy some judgment may be formed from its influence in leading so very acute an inquirer to class number in the same list with solidity and extension. The reader will find some ad

ditional illustrations on the subject of Secondary Qualities in note (L.)

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