5. If all names were definable, it would be a Process IN INFINITUM. I will not here trouble myself to prove that all terms are not definable, from that progress IN INFINITUM, which it will visibly lead us into, if we should allow that all names could be defined. For, if the terms of one definition were still to be defined by another, where at last should we stop? But I shall, from the nature of our ideas, and the signification of our words, show WHY SOME NAMES CAN, AND OTHERS CANNOT BE DEFINED; and WHICH THEY ARE. 6. What a Definition is. I think it is agreed, that a DEFINITION is nothing else but THE SHOWING THE MEANING OF ONE WORD BY SEVERAL OTHER NOT SYNONYMOUS TERMS. The meaning of words being only the ideas they are made to stand for by him that uses them, the meaning of any term is then showed, or the word is defined, when, by other words, the idea it is made the sign of, and annexed to, in the mind of the speaker, is as it were represented, or set before the view of another; and thus its signification ascertained. This is the only use and end of definitions; and therefore the only measure of what is, or is not a good definition. 7. Simple Ideas, why undefinable. This being premised, I say that the NAMES OF SIMPLE IDEAS, AND THOSE ONLY, ARE INCAPABLE OF BEING DEFINED. The reason whereof is this, That the several terms of a definition, signifying several ideas, they can all together by no means represent an idea which has no composition at all: and therefore a definition, which is properly nothing but the showing the meaning of one word by several others not signifying each the same thing, can in the names of simple ideas have no place. 8. Instances: Scholastic definitions of Motion. The not observing this difference in our ideas, and their names, has produced that eminent trifling in the schools, which is so easy to be observed in the definitions they give us of some few of these simple ideas. For, as to the greatest part of them, even those masters of definitions were fain to leave them untouched, merely by the impossibility they found in it. What more exquisite jargon could the wit of man invent, than this definition:--'The act of a being in power, as far forth as in power;' which would puzzle any rational man, to whom it was not already known by its famous absurdity, to guess what word it could ever be supposed to be the explication of. If Tully, asking a Dutchman what BEWEEGINGE was, should have received this explication in his own language, that it was 'actus entis in potentia quatenus in potentia;' I ask whether any one can imagine he could thereby have understood what the word BEWEEGINGE signified, or have guessed what idea a Dutchman ordinarily had in his mind, and would signify to another, when he used that sound? 9. Modern definition of Motion.