PHIL. He is not mistaken with regard to the ideas he actually perceives, but in the inference he makes from his present perceptions. Thus, in the case of the oar, what he immediately perceives by sight is certainly crooked; and so far he is in the right. But if he thence conclude that upon taking the oar out of the water he shall perceive the same crookedness; or that it would affect his touch as crooked things are wont to do: in that he is mistaken. In like manner, if he shall conclude from what he perceives in one station, that, in case he advances towards the moon or tower, he should still be affected with the like ideas, he is mistaken. But his mistake lies not in what he perceives immediately, and at present, (it being a manifest contradiction to suppose he should err in respect of that) but in the wrong judgment he makes concerning the ideas he apprehends to be connected with those immediately perceived: or, concerning the ideas that, from what he perceives at present, he imagines would be perceived in other circumstances. The case is the same with regard to the Copernican system. We do not here perceive any motion of the earth: but it were erroneous thence to conclude, that, in case we were placed at as great a distance from that as we are now from the other planets, we should not then perceive its motion.
HYL. I understand you; and must needs own you say things plausible enough. But, give me leave to put you in mind of one thing. Pray, Philonous, were you not formerly as positive that Matter existed, as you are now that it does not?
PHIL. I was. But here lies the difference. Before, my positiveness was founded, without examination, upon prejudice; but now, after inquiry, upon evidence.
HYL. After all, it seems our dispute is rather about words than things. We agree in the thing, but differ in the name. That we are affected with ideas FROM WITHOUT is evident; and it is no less evident that there must be (I will not say archetypes, but) Powers without the mind, corresponding to those ideas. And, as these Powers cannot subsist by themselves, there is some subject of them necessarily to be admitted; which I call MATTER, and you call SPIRIT. This is all the difference.
PHIL. Pray, Hylas, is that powerful Being, or subject of powers, extended?
HYL. It hath not extension; but it hath the power to raise in you the idea of extension.
PHIL. It is therefore itself unextended?
HYL. I grant it.
PHIL. Is it not also active?
HYL. Without doubt. Otherwise, how could we attribute powers to it?