An Essay Concerning Human Understanding By John Locke Book II: Of Ideas, Chapters 12-33

19. Truth or Falsehood always supposes Affirmation or Negation.

Though, in compliance with the ordinary way of speaking, I have shown in what sense and upon what ground our ideas may be sometimes called true or false; yet if we will look a little nearer into the matter, in all cases where any idea is called true or false, it is from some JUDGMENT that the mind makes, or is supposed to make, that is true or false. For truth or falsehood, being never without some affirmation or negation, express or tacit, it is not to be found but where signs are joined or separated, according to the agreement or disagreement of the things they stand for. The signs we chiefly use are either ideas or words; wherewith we make either mental or verbal propositions. Truth lies in so joining or separating these representatives, as the things they stand for do in themselves agree or disagree; and falsehood in the contrary, as shall be more fully shown hereafter.

20. Ideas in themselves neither true nor false.

Any idea, then, which we have in our minds, whether conformable or not to the existence of things, or to any idea in the minds of other men, cannot properly for this alone be called false. For these representations, if they have nothing in them but what is really existing in things without, cannot be thought false, being exact representations of something: nor yet if they have anything in them differing from the reality of things, can they properly be said to be false representations, or ideas of things they do not represent. But the mistake and falsehood is:

21. But are false — 1. When judged agreeable to another Man's Idea, without being so.

First, when the mind having any idea, it JUDGES and concludes it the same that is in other men's minds, signified by the same name; or that it is conformable to the ordinary received signification or definition of that word, when indeed it is not: which is the most usual mistake in mixed modes, though other ideas also are liable to it.

22. Secondly, When judged to agree to real Existence, when they do not.

(2) When it having a complex idea made up of such a collection of simple ones as nature never puts together, it JUDGES it to agree to a species of creatures really existing; as when it joins the weight of tin to the colour, fusibility, and fixedness of gold.

23. Thirdly, When judged adequate, without being so.

(3) When in its complex idea it has united a certain number of simple ideas that do really exist together in some sort of creatures, but has also left out others as much inseparable, it JUDGES this to be a perfect complete idea of a sort of things which really it is not; v.g. having joined the ideas of substance, yellow, malleable, most heavy, and fusible, it takes that complex idea to be the complete idea of gold, when yet its peculiar fixedness, and solubility in AQUA REGIA, are as inseparable from those other ideas, or qualities, of that body as they are one from another.

24. Fourthly, When judged to represent the real Essence.

(4) The mistake is yet greater, when I JUDGE that this complex idea contains in it the real essence of any body existing; when at least it contains but some few of those properties which flow from its real essence and constitution. I say only some few of those properties; for those properties consisting mostly in the active and passive powers it has in reference to other things, all that are vulgarly known of any one body, of which the complex idea of that kind of things is usually made, are but a very few, in comparison of what a man that has several ways tried and examined it knows of that one sort of things; and all that the most expert man knows are but a few, in comparison of what are really in that body, and depend on its internal or essential constitution. The essence of a triangle lies in a very little compass, consists in a very few ideas: three lines including a space make up that essence: but the properties that flow from this essence are more than can be easily known or enumerated. So I imagine it is in substances; their real essences lie in a little compass, though the properties flowing from that internal constitution are endless.

25. Ideas, when called false.

To conclude, a man having no notion of anything without him, but by the idea he has of it in his mind, (which idea he has a power to call by what name he pleases,) he may indeed make an idea neither answering the reason of things, nor agreeing to the idea commonly signified by other people's words; but cannot make a wrong or false idea of a thing which is no otherwise known to him but by the idea he has of it: v.g. when I frame an idea of the legs, arms, and body of a man, and join to this a horse's head and neck, I do not make a false idea of anything; because it represents nothing without me. But when I call it a MAN or TARTAR, and imagine it to represent some real being without me, or to be the same idea that others call by the same name; in either of these cases I may err. And upon this account it is that it comes to be termed a false idea; though indeed the falsehood lies not in the idea, but in that tacit mental proposition, wherein a conformity and resemblance is attributed to it which it has not. But yet, if, having framed such an idea in my mind, without thinking either that existence, or the name MAN or TARTAR, belongs to it, I will call it MAN or TARTAR, I may be justly thought fantastical in the naming; but not erroneous in my judgment; nor the idea any way false.

26. More properly to be called right or wrong.

Upon the whole matter, I think that our ideas, as they are considered by the mind, — either in reference to the proper signification of their names; or in reference to the reality of things, — may very fitly be called RIGHT or WRONG ideas, according as they agree or disagree to those patterns to which they are referred. But if any one had rather call them true or false, it is fit he use a liberty, which every one has, to call things by those names he thinks best; though, in propriety of speech, TRUTH or FALSEHOOD will, I think, scarce agree to them, but as they, some way or other, virtually contain in them some mental proposition. The ideas that are in a man's mind, simply considered, cannot be wrong; unless complex ones, wherein inconsistent parts are jumbled together. All other ideas are in themselves right, and the knowledge about them right and true knowledge; but when we come to refer them to anything, as to their patterns and archetypes then they are capable of being wrong, as far as they disagree with such archetypes.

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