But in Dublin, all this while, there was a little David practising his youthful strength upon the intellectual lions and bears of Trinity College.  This was George Berkeley, who was destined to give the same kind of development to the idealistic side of Descartes’ philosophy, that the Freethinkers had given to its sceptical side, and the Newtonians to its mechanical side.

Berkeley faced the problem boldly.  He said to the materialists:  “You tell me that all the phenomena of nature are resolvable into matter and its affections.  I assent to your statement, and now I put to you the further question, ‘What is matter?’ In answering this question you shall be bound by your own conditions; and I demand, in the terms of the Cartesian axiom, that in turn you give your assent only to such conclusions as are perfectly clear and obvious.”

It is this great argument which is worked out in the “Treatise concerning the Principles of Human Knowledge,” and in those “Dialogues between Hylas and Philonous,” which rank among the most exquisite examples of English style, as well as among the subtlest of metaphysical writings; and the final conclusion of which is summed up in a passage remarkable alike for literary beauty and for calm audacity of statement.

“Some truths there are so near and obvious to the mind that a man need only open his eyes to see them.  Such I take this important one to be, viz., that all the choir of heaven and furniture of the earth—­in a word, all those bodies which compose the mighty frame of the world—­have not any substance without a mind; that their being is to be perceived or known; that consequently, so long as they are not actually perceived by me, or do not exist in my mind or that of any other created spirit, they must either have no existence at all or else subsist in the mind of some eternal spirit; it being perfectly unintelligible, and involving all the absurdity of abstraction, to attribute to any single part of them an existence independent of a spirit."[1]

[Footnote 1:  “Treatise concerning the Principles of Human Knowledge,” Part I. Sec. 6.]

Doubtless this passage sounds like the acme of metaphysical paradox, and we all know that “coxcombs vanquished Berkeley with a grin;” while common-sense folk refuted him by stamping on the ground, or some such other irrelevant proceeding.  But the key to all philosophy lies in the clear apprehension of Berkeley’s problem—­which is neither more nor less than one of the shapes of the greatest of all questions, “What are the limits of our faculties?” And it is worth any amount of trouble to comprehend the exact nature of the argument by which Berkeley arrived at his results, and to know by one’s own knowledge the great truth which he discovered—­that the honest and rigorous following up of the argument which leads us to materialism, inevitably carries us beyond it.