Locke, John (1632–1704)

2. The structure of Locke’s empiricism

Locke’s mature philosophy is ‘concept-empiricist’, but not ‘knowledge-empiricist’: he held that all our concepts are drawn from experience, but not that all our knowledge is based on experience. Yet his early position, in Essays on the Law of Nature and the first part of Draft A, was ‘knowledge-empiricist’ in just this sense – even the axioms of geometry gain assent ‘only by the testimony and assurance of our senses’ (Draft A I: 22–3). However, according to Draft A, when we find that certain relations hold without exception, we assume that they hold universally and come to employ them as ‘standards’ of measurement embodied in the meaning of our terms. Locke sees this as implying a choice: an axiom can either be interpreted as an ‘instructive’, but uncertain summary of experience, or as a quasi-definition, founded on experience but ‘only verbal…and not instructive’. But later in Draft A he discards the notion that geometrical axioms can be interpreted empirically, taking them only in a sense in which they can be known by ‘demonstration’ or ‘the bare shewing of things or proposing them to our senses or understandings’ (Draft A I: 50) – that is, by intuitions with perceived or imagined instances (for example, diagrams) as their objects. At the same time he recognizes that mathematical propositions are not plausibly regarded as merely verbal. The possibility of alternative interpretations of universal propositions, either as certain, but verbal, or as instructive, but uncertain, is now restricted to propositions about substances, such as ‘Man is rational’. Locke has shifted, in effect, from knowledge-empiricism towards a concept-empiricism which allows ‘instructive’ a priori knowledge (the last being the acknowledged ancestor of Kant’s synthetic a priori – see Kant, I. §4).

Locke’s intuitionism shapes his attack on the innatism characteristic of the Platonic-Augustinian-Cartesian tradition (see Innate knowledge). Starting with propositions, Locke rebuts the argument from alleged universal assent, or assent by all who have come to the use of reason. But ideas are what is before the mind in thought, and propositions are ideas in relation. Locke’s underlying thesis is that to take either knowledge or ideas to be innately ‘imprinted on the mind’ in a merely dispositional sense (and they are clearly not actual in all human beings from birth) would be contrary to any intelligible notion of being ‘in the mind’: ‘Whatever idea was never perceived by the mind, was never in the mind’ (Essay I.iv.20). Locke concedes dispositional knowledge and ideas, retained by the memory and capable of being revived, but he understands both intentionality and knowledge in terms of perception, and finds nonsensical the notion of perception which never has been conscious and actual. This strongly intuitionist model rules out dispositional innatism as an intelligible possibility. Rationalist intuitionism, from Locke’s point of view, is simply incoherent. And since the only dispositional ideas and knowledge are what is retained in the memory, what is before the mind as the object of intuition or demonstration must be experiential or sensory.

Locke also argues that there are no general maxims of logic or mathematics to which all assent when they come to the use of reason, since many rational but illiterate people never consider such abstract principles. He does not accept that reasoning merely consonant with logical principles is equivalent to assent to them, or, for example, that distinguishing two things is tacit employment of the idea of identity. Explicit abstract principles and ideas come late and with so much difficulty that people cannot agree on ideas of impossibility, identity, duty, substance, God and the like – just the ideas most supposed innately luminous. That rational people assent to certain propositions on first proposal is beside the point, since such people will only have understood the terms of the proposition in question by abstraction from experience. Then they will assent, not because the proposition is innate, but because it is evident. To describe the bare capacity to perceive such truths as the possession of innate principles and ideas will make all universal knowledge innate, however specific or derived. Turning to practical principles and the idea of God, Locke appeals to anthropology to rebut the claim that any of these are universally recognized. The main thrust of his argument, however, is conceptual.

Locke’s empiricism has another central feature. Like Gassendi and Hobbes, he expressly accords independent authority to the particular deliverances of the senses (see Gassendi, P. §3). Descartes had argued that sensation requires interpretation employing innate, purely intellectual ideas even in order for us to conceive of its objects as independent bodies. For Descartes, moreover, natural sensory belief is defenceless in the face of sceptical argument – secure knowledge of the existence of bodies can only be achieved through a rational proof involving reflection on the role and mechanisms of sense (see Descartes, R. §9). This emphatic subordination of sense to reason Locke rejects just as firmly: the senses are ‘the proper and sole judges’ of the existence of bodies. He sees the senses as knowledge-delivering faculties in their own right, prior to any understanding of their mechanisms: ‘the actual receiving of ideas from without…makes us know, that something doth exist at that time without us, which causes that idea in us, though perhaps we neither know nor consider how it does it’ (Essay IX.xi.2). The sceptic’s doubt about the external world is a mere pretence, not to be taken seriously: ‘no body can, in earnest, be so sceptical, as to be uncertain of the existence of those things which he sees and feels’. Echoing Lucretius, Locke sees the reason employed in sceptical argument itself as standing or falling with the senses: ‘For we cannot act any thing, but by our faculties; nor talk of knowledge it self, but by the help of those faculties which are fitted to apprehend even what knowledge is’ (Essay IX.xi.3). Locke does identify features of sense-experience which militate against scepticism: for example, sensory ideas depend on physical sense-organs, and are systematically and unavoidably consequent on our situation; the deliverances of different senses cohere; there is a ‘manifest difference’ between ideas of sense and ideas of memory and imagination (most dramatically with respect to pain), as there is between acting in the world and imagining ourselves acting; and so on (Essay IX.xi.4–8). Yet all these considerations are simply ‘concurrent reasons’ which further, but unnecessarily confirm ‘the assurance we have from our senses themselves’ – ‘an assurance that deserves the name of knowledge’ (Essay IX.xi.3).

Locke’s explanation of the certainty and extent of ‘sensitive knowledge of existence’ hinges on his view that in sensation we are immediately aware, not only of sensations or ‘ideas’, but of their being caused by things outside us. We are thus able to think of the unknown cause through its effect in us: ‘whilst I write this, I have, by the paper affecting my eyes, that idea produced in my mind, which, whatever object causes, I call white; by which I know, that that quality or accident (i.e. whose appearance before my eyes, always causes that idea) doth really exist, and hath a being without me’ (Essay IX.xi.2). This claim ties in with another, that ideas of simple sensory qualities are always ‘true’, ‘real’ and ‘adequate’: ‘their truth consists in nothing else, but in such appearances, as are produced in us, and must be suitable to those powers, [God] has placed in external objects, or else they could not be produced in us’ (Essay II.xxxii.14). Simple ideas are ‘distinguishing marks’ which fulfil their function well enough whatever unknown difference lies behind the sensible distinction. But this function fits them for another, as terms in the natural language of thought. The idea of white signifies, that is indicates, its unknown cause, and also signifies, that is stands for, that feature of things in thought. So the limited causal knowledge that sensation supplies allows us to have contentful thought and knowledge of the external world. The idea of power extends such pretheoretical knowledge: our idea of the melting of wax, joined to the idea of active or passive power, can be employed as a sign of whatever in the sun melts wax, or of whatever in wax causes its melting. Consequently Locke decides to treat ideas of powers as simple ideas, and knowledge of powers as observational. The senses do not give knowledge of the essence or nature of bodies, but they do give knowledge of their existence, and enable us to distinguish between them.