Everyone agrees with this opinion about motion, ·namely that it is conceivable only as the motion of something·; and I have proved that it holds also with regard to extension, ·which is conceivable only as the extension of something·—I have shown that it is impossible to conceive extension except as composed of parts that have either colour or solidity. The idea of extension is a compound idea; but it isn’t compounded out of infinitely many parts or lesser ideas, so it must eventually be made up of parts that are perfectly simple and indivisible ·and thus don’t have parts in their turn·. These simple and indivisible parts are not themselves ideas of extension ·because extension must have parts·, so they must be non-entities, nothings, unless they are conceived as coloured or solid. Colour is excluded from any real existence ·by the modern philosophy which I am now examining·. The reality of our •idea of extension therefore depends on the reality of •our idea of solidity; the former can’t be sound if the latter is chimerical. Let us look, then, into the idea of solidity.
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