PHIL. You lay it down as a self-evident principle that the quantity of motion in any body is proportional to the velocity and MATTER taken together; and this is made use of to prove a proposition from whence the existence of MATTER is inferred. Pray is not this arguing in a circle? HYL. In the premise I only mean that the motion is proportional to the velocity, jointly with the extension and solidity. PHIL. But, allowing this to be true, yet it will not thence follow that gravity is proportional to MATTER, in your philosophic sense of the word; except you take it for granted that unknown SUBSTRATUM, or whatever else you call it, is proportional to those sensible qualities; which to suppose is plainly begging the question. That there is magnitude and solidity, or resistance, perceived by sense, I readily grant; as likewise, that gravity may be proportional to those qualities I will not dispute. But that either these qualities as perceived by us, or the powers producing them, do exist in a MATERIAL SUBSTRATUM; this is what I deny, and you indeed affirm, but, notwithstanding your demonstration, have not yet proved. HYL. I shall insist no longer on that point. Do you think, however, you shall persuade me that the natural philosophers have been dreaming all this while? Pray what becomes of all their hypotheses and explications of the phenomena, which suppose the existence of Matter? PHIL. What mean you, Hylas, by the PHENOMENA? HYL. I mean the appearances which I perceive by my senses. PHIL. And the appearances perceived by sense, are they not ideas? HYL. I have told you so a hundred times. PHIL. Therefore, to explain the phenomena, is, to shew how we come to be affected with ideas, in that manner and order wherein they are imprinted on our senses. Is it not? HYL. It is. PHIL. Now, if you can prove that any philosopher has explained the production of any one idea in our minds by the help of MATTER, I shall for ever acquiesce, and look on all that hath been said against it as nothing; but, if you cannot, it is vain to urge the explication of phenomena. That a Being endowed with knowledge and will should produce or exhibit ideas is easily understood. But that a Being which is utterly destitute of these faculties should be able to produce ideas, or in any sort to affect an intelligence, this I can never understand. This I say, though we had some positive conception of Matter, though we knew its qualities, and could comprehend its existence, would yet be so far from explaining things, that it is itself the most inexplicable thing in the world. And yet, for all this, it will not follow that philosophers have been doing nothing; for, by observing and reasoning upon the connexion of ideas, they discover the laws and methods of nature, which is a part of knowledge both useful and entertaining.