On infinite space and its difference from matter
Extension and body not the same. — There are some that would persuade us, that body and extension are the same thing; who either change the signification of words, which I would not suspect them of, they having so severely condemned the philosophy of others, because it hath been too much placed in the uncertain meaning, or deceitful obscurity, of doubtful or insignificant terms. If, therefore, they mean by body and extension, the same that other people do, viz., by body, something that is solid and extended, whose parts are separable and moveable different ways; and by extension, only the space that lies between the extremities of those solid coherent parts, and which is possessed by them, they confound very different ideas one with another. For I appeal to every man's own thoughts, whether the idea of space be not as distinct from that of solidity, as it is from the idea of scarlet colour? It is true, solidity cannot exist without extension, neither can scarlet colour exist without extension; but this hinders not but that they are distinct ideas. Many ideas require others as necessary to their existence or conception, which yet are very distinct ideas. Motion can neither be, nor be conceived, without space; and yet motion is not space, nor space, motion: space can exist without it, and they are very distinct ideas; and so, I think, are those of space and solidity.
Locke, J. (1976)., On infinite space and its difference from matter, in M. Čapek (ed.), The concepts of space and time, Dordrecht, Springer, pp. 107-112.
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