| 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. |
| We may make the same observation concerning mobility and figure; and upon the whole must conclude, that after the exclusion of colours, sounds, heat and cold from the rank of external existences, there remains nothing, which can afford us a just and constituent idea of body. |
| Add to this, that, properly speaking, solidity or impenetrability is nothing, but an impossibility of annihilation, as [Part II. SECT. 4.] has been already observed: For which reason it is the more necessary for us to form some distinct idea of that object, whose annihilation we suppose impossible. |
| An impossibility of being annihilated cannot exist, and can never be conceived to exist, by itself: but necessarily requires some object or real existence, to which it may belong. |
| Now the difficulty still remains, how to form an idea of this object or existence, without having recourse to the secondary and sensible qualities. |
| Nor must we omit on this occasion our accustomed method of examining ideas by considering those impressions, from which they are derived. |
| The impressions, which enter by the sight and hearing, the smell and taste, are affirmed by modern philosophy to be without any resembling objects; and consequently the idea of solidity, which is supposed to be real, can never be derived from any of these senses. |
| There remains, therefore, the feeling as the only sense, that can convey the impression, which is original to the idea of solidity; and indeed we naturally imagine, that we feel the solidity of bodies, and need but touch any object in order to perceive this quality. |
| But this method of thinking is more popular than philosophical; as will appear from the following reflections. |
| First, It is easy to observe, that though bodies are felt by means of their solidity, yet the feeling is a quite different thing from the solidity; and that they have not the least resemblance to each other. |
| A man, who has the palsey in one hand, has as perfect an idea of impenetrability, when he observes that hand to be supported by the table, as when he feels the same table with the other hand. |
| An object, that presses upon any of our members, meets with resistance; and that resistance, by the motion it gives to the nerves and animal spirits, conveys a certain sensation to the mind; but it does not follow, that the sensation, motion, and resistance are any ways resembling. |
| Secondly, The impressions of touch are simple impressions, except when considered with regard to their extension; which makes nothing to the present purpose: And from this simplicity I infer, that they neither represent solidity, nor any real object. |
| For let us put two cases, viz. |