1441 BOOK III. their shapes, would be best let into the mind by draughts1 made of them, and more determine the signification of such words, than any other words set for them, or made use of to define them. But this is only by the bye. CHAP. XI. Fifth To use the 26. V. Fifthly, If men will not be at the pains to declare Remedy: the meaning of their words, and definitions of their terms are same word not to be had, yet this is the least that can be expected, that, constantly in all discourses wherein one man pretends to instruct or in the same sense. When not so used, tion is to be explained. convince another, he should use the same word constantly in the same sense. If this were done, (which nobody can refuse without great disingenuity,) many of the books extant might be spared; many of the controversies in dispute would be at an end; several of those great volumes, swollen with ambiguous words, now used in one sense, and by and by in another, would shrink into a very narrow compass; and many of the philosophers (to mention no other) as well as poets works, might be contained in a nutshell. 27. But after all, the provision of words is so scanty in the Varia- respect to that infinite variety of thoughts, that men, wanting terms to suit their precise notions, will, notwithstanding their utmost caution, be forced often to use the same word in somewhat different senses. And though in the continuation of a discourse, or the pursuit of an argument, there can be hardly room to digress into a particular definition, as often as a man varies the signification of any term; yet the import of the discourse will, for the most part, if there be no designed fallacy, sufficiently lead candid and intelligent readers into the true meaning of it 2; but where there is not sufficient to guide the reader, there it concerns the writer to explain his meaning, and show in what sense he there uses that term. 1 'draughts'-pictures, which exercise the sensuous imagination instead of the abstracting intellect. 2 This must be remembered in the interpretation of Locke's own Essay. SYNOPSIS OF THE FOURTH BOOK. Locke's review of the different sorts of ideas, or appearances of what exists, that can be entertained in a human understanding, and of their relations to words, leads, in the Fourth Book, to an investigation of the extent and validity of the Knowledge that our ideas bring within our reach; and into the nature of faith in Probability, by which assent is extended beyond Knowledge, for the conduct of life. He finds (chh. i, ii) that Knowledge is either an intuitive, a demonstrative, or a sensuous perception of absolute certainty, in regard to one or other of four sorts of agreement or disagreement on the part of ideas:(1) of each idea with itself, as identical, and different from every other; (2) in their abstract relations to one another; (3) in their necessary connexions, as qualities and powers coexisting in concrete substances; and (4) as revelations to us of the final realities of existence. The unconditional certainty that constitutes Knowledge is perceptible by man only in regard to the first, second, and fourth of these four sorts: in all general propositions only in regard to the first and second; that is to say, in identical propositions, and in those which express abstract relations of simple or mixed modes, in which nominal and real essences coincide, e. g. propositions in pure mathematics and abstract morality (chh. iii, v-viii). The fourth sort, which express certainty as to realities of existence, refer to any of three realities. For every man is able to perceive with absolute certainty that he himself exists, that God must exist, and that finite beings other than himself exist;—the first of these perceptions being awakened by all our ideas, the second as the consequence of perception of the first, and the last in the reception of our simple ideas of sense (chh. i. § 7; ii. § 14; iii. § 21; iv, ix-xi). Agreement of the third sort, or necessary coexistence of simple ideas as qualities and powers in particular substances, with which all physical inquiry is concerned, lies beyond human Knowledge; for here the nominal and real essences are not coincident: general propositions of this sort are determined by analogies of experience, in judgments that are more or less probable: intellectually necessary science of nature presupposes Omniscience; man's interpretations of nature have to turn upon presumptions of Probability (chh. iii. §§ 9-17; iv. §§ 11-17; vi, xiv-xvi). In forming their stock of Certainties and Probabilities men employ the faculty of reason, faith in divine revelation, and enthusiasm (chh. xvii-xix); much misled by the last, as well as by other causes of 'wrong assent' (ch. xx), when they are at work in 'the three great provinces of the intellectual world' (ch. xxi), concerned respectively with (1) 'things as knowable' (physica); (2) ‘actions as they depend on us in order to happiness' (practica); and (3) methods for interpreting the signs of what is, and of what ought to be, that are presented in our ideas and words (logica). CHAPTER I. OF KNOWLEDGE IN GENERAL. 1441 CHAP. I. Our 1. SINCE the mind, in all its thoughts and reasonings, hath BOOK IV. no other immediate object but its own ideas, which it alone does or can contemplate, it is evident that our knowledge is only conversant about them 1. 2. Knowledge then seems to me to be nothing but the ledge conperception of the connexion of and agreement, or disagreement and about our repugnancy of any of our ideas. In this alone it consists. Ideas only. 1 In thus limiting human knowledge to the simple ideas presented by substances, in the senses and in reflection; their abstracted modes, simple and mixed; our complex ideas of substances, and their abstract relations, Locke does not say that human faith is equally confined to what men can have positive ideas of. 'A great many things,' he elsewhere says, 'may be, and are granted to have a being, and be in nature, of which we have no ideas. For example, it cannot be doubted that there are distinct species of separate spirits, of which yet we have no distinct ideas at all: it cannot be questioned but that spirits have ways of communicating their thoughts, and yet we have no idea of it at all.' (First Letter to Stillingfleet, p. 83; see also Third Letter, pp. 245-47.) The belief in the existence of colours in their variations, which a born-blind man can have, though he can have no ideas of them, to which Locke elsewhere refers, is a more patent proof that faith is wider than knowledge; and that belief in the existence of a thing may consist with our having the 'simple idea of its existence' only, without distinct ideas of what the thing is. 2 Cf. ch. xiv. §§ 3, 4. Locke has been blamed for unduly limiting the application of the terms knowledge and judgment, by confining the former to 'perceptions,' in which unconditional certainty is intellectually visible, and the latter to the conditional assurance that is naturally caused by presumptions of probability only. To which Reid for example objects, that 'the far greatest part of what all men call human knowledge is in things which neither admit of intuitive nor demonstrative proof. And by judgment I understand that operation of mind by which we determine concerning anything that may be expressed by a proposition, whether it be true or false. A proposition may be simply conceived, without judging of it. But when there is not only a conception of the proposition, but a mental affirmation or Know versant CHAP. I. Knowledge is the Perception of the Agree BOOK IV. Where this perception1 is, there is knowledge, and where it is not, there, though we may fancy, guess, or believe, yet we always come short of knowledge. For when we know that white is not black, what do we else but perceive, that these two ideas do not agree? When we possess ourselves with the utmost security of the demonstration, that the three angles of a triangle are equal to two right ones, what do we more but perceive, that equality to two right ones does two Ideas, necessarily agree2 to, and is inseparable from, the three angles of a triangle? ment or Disagree ment of This 3. But to understand a little more distinctly wherein this agreement or disagreement consists, I think we may reduce it Disagree all to these four sorts: ment or ment may be any of four sorts. I. Identity, or diversity. II. Relation. III. Co-existence, or necessary connexion. IV. Real existence 3. negation, an assent or dissent of the It is also important to note that he makes 'mental proposition' (i. e. judgment, in its wider meaning) the unit of knowledge and assent, as distinguished from mere idea, simple or complex. Everything which we either know or believe is some [mental] proposition.' (Third Letter to Stillingfleet, p. 245.) And as all propositions imply terms, even belief presupposes at least the idea of 'existence' to be predicable of what is believed to exist, without (it may be) any positive idea of what the existing being is. |