| The idea of motion necessarily supposes that of a body moving. |
| Now what is our idea of the moving body, without which motion is incomprehensible? It must resolve itself into the idea of extension or of solidity; and consequently the reality of motion depends upon that of these other qualities. |
| This opinion, which is universally acknowledged concerning motion, I have proved to be true with regard to extension; and have shewn that it is impossible to conceive extension, but as composed of parts, endowed with colour or solidity. |
| The idea of extension is a compound idea; but as it is not compounded of an infinite number of parts or inferior ideas, it must at last resolve itself into such as are perfectly simple and indivisible. |
| These simple and indivisible parts, not being ideas of extension, must be non entities, unless conceived as coloured or solid. |
| Colour is excluded from any real existence. |
| The reality, therefore, of our idea of extension depends upon the reality of that of solidity, nor can the former be just while the latter is chimerical. |
| Let us, then, lend our attention to the examination of the idea of solidity. |
| The idea of solidity is that of two objects, which being impelled by the utmost force, cannot penetrate each other; but still maintain a separate and distinct existence. |
| Solidity, therefore, is perfectly incomprehensible alone, and without the conception of some bodies, which are solid, and maintain this separate and distinct existence. |
| Now what idea have we of these bodies? The ideas of colours, sounds, and other secondary qualities are excluded. |
| The idea of motion depends on that of extension, and the idea of extension on that of solidity. |
| It is impossible, therefore, that the idea of solidity can depend on either of them. |
| For that would be to run in a circle, and make one idea depend on another, while at the same time the latter depends on the former. |
| Our modern philosophy, therefore, leaves us no just nor satisfactory idea of solidity; nor consequently of matter. |
| This argument will appear entirely conclusive to every one that comprehends it; but because it may seem abstruse and intricate to the generality of readers, I hope to be excused, if I endeavour to render it more obvious by some variation of the expression. |
| In order to form an idea of solidity, we must conceive two bodies pressing on each other without any penetration; and it is impossible to arrive at this idea, when we confine ourselves to one object, much more without conceiving any. |
| Two non-entities cannot exclude each other from their places; because they -never possess any place, nor can be endowed with any quality. |
| Now I ask, what idea do we form of these bodies or objects, to which we suppose solidity to belong? To say, that we conceive them merely as solid, is to run on in infinitum. |
| To affirm, that we paint them out to ourselves as extended, either resolves all into a false idea, or returns in a circle. |
| Extension must necessarily be considered either as coloured, which is a false idea; I or as solid, which brings us back to the first question. |