hand* which has illustrated and adorned his geological researches, would undertake the task of guiding us through the puzzling, but interesting labyrinth of his metaphysical discussions.

The following is the conclusion of Dr. Hutton's argument concerning Hardness and Incompressibility:

"In thus distinguishing things, it will appear 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 resistance 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 properties of the body are, with all the certainty of human observation, known to be changed.

"But if the resistance which is opposed by a natural body to the exertion of our will, endeavouring to destroy the volume, should be as perfectly overcome as is that of hardness in fluidity, then the common opinion of mankind, which supposes the extension of a body to be permanent, would necessarily be changed. For at present, we think that this resisting power, which preserves volume in bodies, is absolutely in its nature insurmountable, as it certainly is in relation to our moving power.

"Instead, then, of saying that Matter, of which natural bodies are composed, is perfectly hard and impenetrable, which is the received opinion of philosophers, we would affirm, that * [Mr. Playfair is meant.—Ed.]

VOL. V.

G

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 destroyed."1

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, 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."2

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 Extension 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 Extension. It is therefore superfluous to inquire particularly concerning each of them. In denying Extension, you have denied them all to have any real existence."3

That Dr. Hutton's opinion concerning Magnitude and Figure

Dissertations on different subjects in Natural Philosophy, pp. 289, 290.

[First Dialogue between Hylas and

Philonous,] Berkeley's Works, [London or] Dublin edition of 1784; vol. i. p. 133. 3 Ibid. vol. i. p. 133.

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 conclusion, that Magnitude and Figure do not exist externally in relation to the mind, follows naturally as a consequence of both.”

"It is, indeed," he continues, "a necessary consequence of both theories, that Magnitude and Figure do not exist in nature, 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." "1

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 con-nexion which Dr. Hutton had supposed between his own physical conclusions concerning 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 been made to the validity 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 1 Hutton's Principles of Knowledge, vol. i. p. 357.

* [Pp. 95, 96.]

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.

CHAPTER II.

[ON OUR BELIEF OF THE EXISTENCE OF THE MATERIAL WORLD.]

SECTION I.-ON THE FOUNDATION OF OUR BELIEF OF THE EXISTENCE OF THE MATERIAL WORLD, ACCORDING TO THE STATEMENT OF REID.-STRICTURES ON THAT STATEMENT.

I HAVE already said, that Reid's account of the existence of Matter, although correct so far as it goes, does not embrace all the circumstances of the question. The grounds of this observation I shall endeavour to explain with all possible brevity; but, before proceeding to the discussion, it is necessary to premise some remarks on a principle of our constitution, which may at first sight appear very foreign to the present argument; I mean, our belief of the permanence or stability of the order of nature.

That all our physical reasonings, and all those observations on the course of events, which lay the foundation of foresight or sagacity, imply an expectation, that the order of things will, in time to come, continue similar to what we have experienced it to be in time past, is a fact too obvious to stand in need of illustration; but it is not equally clear how this expectation arises at first in the mind. Mr. Hume resolves it into the association of ideas, which leads us, after having seen two events often conjoined, to anticipate the second, whenever we see the first:—a theory to which a very strong objection immediately presents itself, That a single experiment is sufficient to create as strong a belief of the constancy of the result as ten thousand. When a philosopher repeats an experiment for the sake of greater certainty, his hesitation does not proceed from.