77.  That A substratum not perceived, may exist, unimportant.—­But, say you, though it be granted that there is no thoughtless support of extension and the other qualities or accidents which we perceive, yet there may perhaps be some inert, unperceiving substance or substratum of some other qualities, as incomprehensible to us as colours are to a man born blind, because we have not a sense adapted to them.  But, if we had a new sense, we should possibly no more doubt of their existence than a blind man made to see does of the existence of light and colours.  I answer, first, if what you mean by the word Matter be only the unknown support of unknown qualities, it is no matter whether there is such a thing or no, since it no way concerns us; and I do not see the advantage there is in disputing about what we know not what, and we know not why.

78.  But, secondly, if we had a new sense it could only furnish us with new ideas or sensations; and then we should have the same reason against their existing in an unperceiving substance that has been already offered with relation to figure, motion, colour and the like.  Qualities, as has been shown, are nothing else but sensations or ideas, which exist only in a mind perceiving them; and this is true not only of the ideas we are acquainted with at present, but likewise of all possible ideas whatsoever.

79.  But, you will insist, what if I have no reason to believe the existence of Matter? what if I cannot assign any use to it or explain anything by it, or even conceive what is meant by that word? yet still it is no contradiction to say that Matter exists, and that this Matter is in general a substance, or occasion of ideas; though indeed to go about to unfold the meaning or adhere to any particular explication of those words may be attended with great difficulties.  I answer, when words are used without a meaning, you may put them together as you please without danger of running into a contradiction.  You may say, for example, that twice two is equal to seven, so long as you declare you do not take the words of that proposition in their usual acceptation but for marks of you know not what.  And, by the same reason, you may say there is an inert thoughtless substance without accidents which is the occasion of our ideas.  And we shall understand just as much by one proposition as the other.

80.  In the last place, you will say, what if we give up the cause of material Substance, and stand to it that Matter is an unknown somewhat—­neither substance nor accident, spirit nor idea, inert, thoughtless, indivisible, immovable, unextended, existing in no place.  For, say you, whatever may be urged against substance or occasion, or any other positive or relative notion of Matter, has no place at all, so long as this negative definition of Matter is adhered to.  I answer, you may, if so it shall seem good, use the word “Matter” in the same sense as other men use “nothing,” and so make those terms convertible in your style.  For, after all, this is what appears to me to be the result of that definition, the parts whereof when I consider with attention, either collectively or separate from each other, I do not find that there is any kind of effect or impression made on my mind different from what is excited by the term nothing.