case than the Indian before mentioned, who, urging that the world was supported by a great elephant, was asked what the elephant rested on? to which his answer was, a great tortoise.  But being again pressed to know what gave support to the broad-backed tortoise I replied, something, he knew not what.  And thus here, as in all other cases when we use words without having clear and distinct ideas, we talk like children, who, being questioned what such a thing is, readily give this satisfactory answer, that it is something; which in truth signifies no more when so used, either by children or men, but that they know not what, and that the thing they pretend to talk and know of is what they have no distinct idea of at all, and are, so, perfectly ignorant of it and in the dark.  The idea, then, we have, to which we give the general name substance, being nothing but the supposed but unknown support of those qualities we find existing, which we imagine cannot exist sine re substante, without something to support them, we call that support substantia, which, according to the true import of the word, is, in plain English, standing under or upholding."[1]

[Footnote 1:  Locke, “Human Understanding,” Book II. chap, xiii.  Sec. 2.]

I cannot but believe that the judgment of Locke is that which Philosophy will accept as her final decision.

Suppose that a piano were conscious of sound, and of nothing else.  It would become acquainted with a system of nature entirely composed of sounds, and the laws of nature would be the laws of melody and of harmony.  It might acquire endless ideas of likeness and unlikeness, of succession, of similarity and dissimilarity, but it could attain to no conception of space, of distance, or of resistance; or of figure, or of motion.

The piano might then reason thus:  All my knowledge consists of sounds and the perception of the relations of sounds; now the being of sound is to be heard; and it is inconceivable that the existence of the sounds I know, should depend upon any other existence than that of the mind of a hearing being.

This would be quite as good reasoning as Berkeley’s, and very sound and useful, so far as it defines the limits of the piano’s faculties.  But for all that, pianos have an existence quite apart from sounds, and the auditory consciousness of our speculative piano would be dependent, in the first place, on the existence of a “substance” of brass, wood, and iron, and, in the second, on that of a musician.  But of neither of these conditions of the existence of his consciousness would the phenomena of that consciousness afford him the slightest hint.

So that while it is the summit of human wisdom to learn the limit of our faculties, it may be wise to recollect that we have no more right to make denials, than to put forth affirmatives, about what lies beyond that limit.  Whether either mind, or matter, has a “substance” or not, is a problem which we are incompetent to discuss; and it is just as likely that the common notions upon the subject should be correct as any others.  Indeed, Berkeley himself makes Philonous wind up his discussions with Hylas, in a couple of sentences which aptly express this conclusion:—­