An Essay Concerning Human Understanding By John Locke Book III: Of Words



1. Names of simple Ideas, Modes, and Substances, have each something peculiar.

Though all words, as I have shown, signify nothing immediately but the ideas in the mind of the speaker; yet, upon a nearer survey, we shall find the names of SIMPLE IDEAS, MIXED MODES (under which I comprise RELATIONS too), and NATURAL SUBSTANCES, have each of them something peculiar and different from the other. For example: —

2. First, Names of simple Ideas, and of Substances intimate real Existence.

First, the names of SIMPLE IDEAS and SUBSTANCES, with the abstract ideas in the mind which they immediately signify, intimate also some real existence, from which was derived their original pattern. But the names of MIXED MODES terminate in the idea that is in the mind, and lead not the thoughts any further; as we shall see more at large in the following chapter.

3. Secondly, Names of simple Ideas and Modes signify always both real and nominal Essences.

Secondly, The names of simple ideas and modes signify always the real as well as nominal essence of their species. But the names of natural substances signify rarely, if ever, anything but barely the nominal essences of those species; as we shall show in the chapter that treats of the names of substances in particular.

4. Thirdly, Names of simple Ideas are undefinable.

Thirdly, The names of simple ideas are not capable of any definition; the names of all complex ideas are. It has not, that I know, been yet observed by anybody what words are, and what are not, capable of being defined; the want whereof is (as I am apt to think) not seldom the occasion of great wrangling and obscurity in men's discourses, whilst some demand definitions of terms that cannot be defined; and others think they ought not to rest satisfied in an explication made by a more general word, and its restriction, (or to speak in terms of art, by a genus and difference,) when, even after such definition, made according to rule, those who hear it have often no more a clear conception of the meaning of the word than they had before. This at least I think, that the showing what words are, and what are not, capable of definitions, and wherein consists a good definition, is not wholly besides our present purpose; and perhaps will afford so much light to the nature of these signs and our ideas, as to deserve a more particular consideration.

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.

Nor have the modern philosophers, who have endeavoured to throw off the jargon of the schools, and speak intelligibly, much better succeeded in defining simple ideas, whether by explaining their causes, or any otherwise. The atomists, who define motion to be 'a passage from one place to another,' what do they more than put one synonymous word for another? For what is PASSAGE other than MOTION? And if they were asked what passage was, how would they better define it than by motion? For is it not at least as proper and significant to say, Passage is a motion from one place to another, as to say, Motion is a passage, &c.? This is to translate, and not to define, when we change two words of the same signification one for another; which, when one is better understood than the other, may serve to discover what idea the unknown stands for; but is very far from a definition, unless we will say every English word in the dictionary is the definition of the Latin word it answers, and that motion is a definition of MOTUS. Nor will 'the successive application of the parts of the superficies of one body to those of another,' which the Cartesians give us, prove a much better definition of motion, when well examined.

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