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“ that incompressibility and hardness, i. e. powers “resisting the change of volume and figure, are the “ properties of an external body; and that these are “ the essential qualities of that extended, figured “thing, so far as it is only in these resisting powers “that the conceived thing, termed body, is judged “ to subsist. - - “But these properties of body, or those powers, “are not found to be absolute; so far as a hard “body may be either broken or made soft, and so “far as, by compression, a body may be diminished “in its volume. “Hence, the judgment that has been formed “from the resistance of the external thing, is, in “some measure, to be changed; and that first “ opinion, with regard to apparent permanency, “ which might have been formed from the resist‘ance of the perceived thing, must now yield to “ the positive testimony of the sense, whereby the “body is perceived to be actually diminished. That “ power of resistance, therefore, from whence a “state of permanency had been concluded, is now “found to be overcome; and those apparent pro“perties of the body are, with all the certainty of “human observation, known to be changed. “But if the resistance, which is opposed by a natu“ral body to the exertion of our will, endeavouring “to destroy the volume, should be as perfectly over“come as is that of hardness in fluidity, then the “ common opinion of mankind, which supposes the “extension of a body to be permanent, would ne
“cessarily be changed. For, at present, we think “that this resisting power, which preserves volume “ in bodies, is absolutely in its nature insurmount“able, as it certainly is in relation to our moving “power. “Instead, then, of saying that matter, of which “matural bodies are composed, is perfectly hard and “impenetrable, which is the received opinion of “ philosophers, we would affirm, that there is no “permanent property of this kind in a material “thing, but that there are certain resisting powers “in bodies, by which their volumes and figures are “presented to us in the actual information; which “powers, however, might be overcome. In that “case, the extension of the most solid body would “be considered only as a conditional thing, like the “hardness of a body of ice; which hardness is, in “the aqueous state of that body, perfectly destroy“ ed.” “ All this coincides perfectly with the opinions of Boscovich ; and it must, I think, appear conclusive to every person who reflects on the subject with due attention. Nor is there anything in the doctrine here maintained repugnant to the natural apprehensions of the mind; or requiring, for its comprehension, habits of metaphysical refinement. Indeed, it amounts to nothing more than to the following incontestable remark, long before made by Berkeley, “ that both hardness and resistance,”
* Dissertations on different subjects in Nattiral Philosophy, pp. 289 and 290. 7
which words he considers as perfectly synonymous with solidity, “are plainly relative to our senses; “it being evident, that what seems hard to one “ animal, may appear soft to another, who hath “greater force and firmness of limbs.” " The case, however, is very different, when we find Dr Berkeley and Dr Hutton attempting to place extension and figure on the same footing with hardness and resistance. The former of these writers seems to have considered the ideal existence of eartension as still more manifest than that of solidity ; having employed the first of these propositions as a medium of proof for the establishment of the other. “If extension be once acknowledged “ to have no existence without the mind, the same “must necessarily be granted of motion, solidity, “ and gravity, since they all evidently suppose ex“tension. It is therefore superfluous to inquire “ particularly concerning each of them. In deny“ing extension, you have denied them all to have “any real existence,” t That Dr Hutton's opinion concerning magnitude and figure coincided exactly with that of Berkeley, appears not only from the general scope of his Theory of Perception, but from the account which he himself has given of the various particulars by which he conceived that theory to be discriminated from the Berkeleian system. “It may now,” says he, “be proper to observe, that the theory here
“given of perception, although at first sight it may “be thought similar to that of Dr Berkeley, will “be found to differ from it, both in its nature and “in its operation upon science; although the con“clusion, that magnitude and figure do not eatist “eaternally in relation to the mind, follows natu“rally as a consequence of both.” “It is, indeed,” he continues, “a necessary con“sequence of both theories, that magnitude and “figure do not exist in mature, or subsist externally, . “but that these are purely spiritual, or ideas in the “mind: This, however, is the only point in which “ the two theories agree.” " It would be altogether foreign to my present purpose to attempt to follow the very ingenious author through the elaborate exposition which he has given of the characteristical peculiarities of his own doctrine. I have studied it with all the attention in my power, but without being able fully to comprehend its meaning. As far as I can judge, the obscurity which hangs over it arises, in a great measure, from a mistaken connection which Dr Hutton had supposed between his own physical conclusions.comcerning hardness, or relative incompressibility, and Berkeley’s metaphysical argument against the independent existence of things external. How clearly this distinction was seized by Boscovich, is demonstrated by a passage already quoted: And accordingly, it may be remarked, that, notwithstanding the numerous objections which have beg. made to the
* Hutton's Principles of Knowledge, Vol. I. p. 357.
yalidity of his reasonings, none of his critics has refused him the praise of the most luminous perspicuity. The truth is, that, while the conclusions of Boscovich and of Hutton, with respect to matter, so far as hardness or relative incompressibility is concerned, offer no violence to the common judgments of mankind, but only aim at a more correct and scientific statement of the fact than is apt to occur to our first hasty apprehensions,—the assertion of Berkeley, that extension and figure have merely an ideal or (as Dr Hutton calls it) a spiritual existence, tends to unhinge the whole frame of the human understanding, by shaking our confidence in those principles of belief which form an essential part of its constitution. But on this point I shall have an opportunity of explaining myself more fully, in the course of some observations which I propose to offer on the philosophy of Dr Reid.