that the whole is bigger than a part; and that two and two are equal to four. The truth of these, and the like propofitions, we know by a bare fimple intuition of the ideas themselves, without any more ado; and fuch propofitions are called selfvident. The mediate perception of the agreement, or difagreement, of two ideas, is when, by the intervention of one or more other ideas, their agreement, or disagreement, is fhown. This is called demonftration, or rational knowledge. For inftance: The inequality of the breadth of two windows, or two rivers, or any two bodies that cannot be put together, may be known by the intervention of the fame meafure, applied to them both; and fo it is in our general ideas, whofe agreement or difagreement may be often fhown by the intervention of fome other ideas, fo as to produce demonftrative knowledge; where the ideas in queftion cannot be brought together, and immediately compared, fo as to produce intuitive knowledge. The understanding doth not know only certain truth ; but alfo judges of probability, which confifts in the likely agreement, or difagreement, of ideas. The affenting to any propofition as probable is called opinion, or belief. We have hitherto confidered the great and visible parts of the univerfe, and thofe great maffes of matter, the ftars, planets, and particularly this our earth, together with the inanimate parts, and animate inhabitants of it; it may be now fit to confider what these fenfible bodies are made of, and that is of unconceivably small bodies, or atoms, out of whofe various combinations bigger moleculæ are made: and fo, by a greater and greater compofition, bigger bodies; and out of these the whole material world is conftituted. . By the figure, bulk, texture, and motion, of these fmall and infenfible corpufcles, all the phænomena of bodies may be explained. A NEW EPISTOLA.] A letter from Mr. Locke to Mr. 2. Toignard, containing a new and easy method of a common-place-book, to which an index. of two pages is fufficient. A T length, fir, in obedience to you, I publish my "method of a common-place-book." I am afhamed that I deferred fo long complying with your request; but I esteemed it fo mean a thing, as not to deserve publishing, in an age fo full of ufeful inventions, as ours is. You may remember, that I freely communicated it to you, and feveral others, to whom I imagined it would not be unacceptable: fo that it was not to reserve the fole use of it to myself, that I declined publishing it. But the regard I had to the public difcouraged me from prefenting it with fuch a trifle. Yet my obligations to you, and the friendship between us, compel me now to follow your advice. Your last letter has perfectly determined me to it, and I am convinced that I ought not to delay publishing it, when you tell me, that an experience of feveral years has fhowed its usefulness, and feveral of your friends, to whom you have communicated it. There is no need I should tell you, how useful it has been to me, after five and twenty years experience, as I told you, eight years fince, when I had the honour to wait on you at Paris, and when I might have been inftructed, by your learned and agreeable difcourfe. What I aim at now, by this letter, is to teftify publicly the esteem and refpect I have for you, and to convince you how much I am, fir, your, &c. Before I enter on my fubject, it is fit to acquaint the reader, that this tract is disposed in the fame manner that the common-place-book ought |