Abstract

Although they differed about the intellect and the nature of ideas, Locke's account of demonstrative reasoning is very similar to Descartes's account of deduction. Locke's demonstration is unlike both syllogistic and modern versions of deduction. It is not formal; the quality of a demonstration depends on the content of the ideas seen to be related. Like Descartes, Locke has an account of demonstration based on intuition. In some cases, one intuitively perceives the connection between two ideas. In other cases, one constructs a chain of ideas such that one indirectly perceives the connection between two ideas at the ends of the chain by directly or intuitively perceiving the connection between any idea in the chain and its neighbour. There is no probable analogue in Locke to intuition. There are no direct beliefs; all beliefs are the result of probable reasoning or judgement. The connection between two ideas is presumed, rather than perceived, in belief. This presumption is caused by the evidence for the belief.