ABSTRACT
Locke’s tripartite division of knowledge by reference to its sources in intuition, reason (or ‘demonstration’) and experience is a traditional one, widely adopted by other seventeenth-century philosophers. But he combines it with the somewhat peculiar and obscure doctrine that knowledge consists in our ‘Perception of the Agreement, or Disagreement, of any of our Ideas’ (4.3.1). This seems at best a way of characterising certain examples of what he calls ‘intuitive’ knowledge and is difficult to extend, without considerable strain, to other areas of knowledge. The kinds of examples in question are those provided by Locke in passages such as the following:
[S]ometimes the Mind perceives the Agreement or Disagreement of two Ideas immediately …. And this … we may call intuitive Knowledge …. Thus the Mind perceives, that White is not Black, That a Circle is not a Triangle, That Three are more than Two, and equal to One and Two.
(4.2.1) The ‘ideas’ of white and black would seem to ‘disagree’ just in the sense that one cannot perceive a surface as being, at one and the same time, both black and white, just as one cannot perceive it as being both red and green – although whether this ‘cannot’ expresses a merely psychological impossibility, or something stronger, is open to debate. Such a ‘disagreement’ is not apparently a logical disagreement, in the sense that a formal contradiction can be derived from the statement ‘S is both black and white’, when suitable definitions of ‘black’ and/or ‘white’ are provided: for, according to Locke, our ideas of black and white are simple and therefore unanalysable – a claim which does indeed have considerable plausibility. ‘White’ plainly does not mean ‘not black’, since red is neither black nor white. Nor does it mean ‘not black nor any chromatic colour’, for – even if we could non-circularly define ‘chromatic colour’ – grey is neither black nor white nor any chromatic colour. Nor does it mean ‘not black nor grey nor any chromatic colour’ – since a transparent surface can come under none of these descriptions and yet not be white either. And so it goes on.