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. CHAP. I. Our I. 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 ideas2. In this alone it consists. Ideas only. 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 Agree. 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. sity in 4. First, As to the first sort of agreement or disagreement, BOOK IV. viz. identity or diversity. It is the first act of the mind, when CHAP. I. it has any sentiments or ideas at all, to perceive its ideas; First, Of and so far as it perceives them, to know each what it is, and Identity, thereby also to perceive their difference, and that one is not or Diveranother. This is so absolutely necessary, that without it ideas. there could be no knowledge, no reasoning, no imagination, no distinct thoughts at all. By this the mind clearly and infallibly perceives each idea to agree with itself, and to be what it is; and all distinct ideas to disagree, i. e. the one not to be the other: and this it does without pains, labour, or deduction; but at first view, by its natural power of perception and distinction. And though men of art have reduced this into those general rules, What is, is, and It is impossible for the same thing to be and not to be, for ready application in all cases, wherein there may be occasion to reflect on it: yet it is certain that the first exercise of this faculty is about particular ideas2. A man infallibly knows, as soon as ever he has them in his mind, that the ideas he calls white and round are the very ideas they are; and that they are not other ideas which he calls red or square. Nor can any maxim or proposition in the world make him know it clearer or surer than he did before, and without any such general rule3. This then is the first agreement or disagree of the sorts of mental propositions, into which our ideas can enter as terms. Locke next wants to determine in which of them the certainty that makes knowledge, and in which only probability, is attainable. The classification itself is crude and hardly logical. Agreement or disagreement' is in all cases relation; yet 'relation' is the second member of the division. The analysis and classification may be compared with Kant's analytic and synthetic (a priori and a posteriori) judgments, and with his dialectical inferences of pure Reason. 1 Consciousness necessarily implies contrast. Omnis determinatio est negatio. We apprehend a circle by a mental negation of every other figure. 3 Yet the after recognition by the CHAP. I. BOOK IV. ment which the mind perceives in its ideas; which it always perceives at first sight: and if there ever happen any doubt about it, it will always be found to be about the names1, and not the ideas themselves, whose identity and diversity will always be perceived, as soon and clearly as the ideas themselves are; nor can it possibly be otherwise. Relations ideas. Secondly, 5. Secondly, the next sort of agreement or disagreement Of abstract the mind perceives in any of its ideas may, I think, be called between relative 2, and is nothing but the perception of the relation between any two ideas, of what kind soever, whether substances, modes, or any other. For, since all distinct ideas must eternally be known not to be the same, and so be universally and constantly denied one of another, there could be no room for any positive knowledge at all, if we could not perceive any relation between our ideas, and find out the agreement or disagreement they have one with another, in several ways the mind takes of comparing them. Thirdly, necessary 6. Thirdly, The third sort of agreement or disagreement to Of their be found in our ideas, which the perception of the mind is Co-exist- employed about, is co-existence or non-co-existence in the same subject; and this belongs particularly to substances. Thus when we pronounce concerning gold, that it is fixed, our knowledge of this truth amounts to no more but this, that fixedness, or a power to remain in the fire unconsumed, is ence in Sub stances. in concrete substances, or (c) the ultimate realities which they reveal. Cf. Hume's Treatise, Pt. I, Sect. v. 3 Locke's 'relation' (§ 5) means abstract relation (e. g. in pure mathematics), independent of place and time -in other words of change, and of the imperfectly known powers and laws by which changes are determined. It virtually includes the a priori synthetic judgments recognised in Kant's more critical analysis. Propositions of 'coexistence' are those which concern concrete substances, constituting physics, and consisting of synthetic judgments-reached a posteriori, or by observation and inductive generalisation, according to Locke. |