First, it has been said against Spinoza, according to the scholastic way of talking, rather than thinking, that a mode, not being any distinct or separate existence, must be the very same with its substance, and consequently the extension of the universe must be in a manner identified with that simple, uncompounded essence in which the universe is supposed to inhere. But this, it may be pretended, is utterly impossible and inconceivable unless the indivisible substance expand itself, so as to correspond to the extension, or the extension contract itself, so as to answer to the indivisible substance. This argument seems just, as far as we can understand it; and 'tis plain nothing is required, but a change in the terms, to apply the same argument to our extended perceptions, and the simple essence of the soul; the ideas of objects and perceptions being in every respect the same, only attended with the supposition of a difference, that is unknown and incomprehensible. Secondly, it has been said, that we have no idea of substance, which is not applicable to matter; nor any idea of a distinct substance, which is not applicable to every distinct portion of matter. Matter therefore is not a mode but a substance, and each part of matter is not a distinct mode, but a distinct substance. I have already proved, that we have no perfect idea of substance; but that taking it for _something that can exist by itself_, 'tis evident every perception is a substance, and every distinct part of a perception a distinct substance: and consequently the one hypothesis labours under the same difficulties in this respect with the other. Thirdly, it has been objected to the system of one simple substance in the universe, that this substance, being the support or _substratum_ of every thing, must at the very same instant be modified into forms, which are contrary and incompatible. The round and square figures are incompatible in the same substance at the same time. How then is it possible, that the same substance can at once be modified into that square table, and into this round one? I ask the same question concerning the impressions of these tables; and find that the answer is no more satisfactory in one case than in the other.