Locke on knowledge and certainty

Locke defines knowledge as ‘the perception of the connexion and agreement, or disagreement and repugnancy of any of our Ideas’ (Essay 4.1.2 525). This chapter examines the implications of each part of this definition: why Locke thinks of knowledge as a kind of perceiving, and what he thinks it is to perceive that ideas agree or disagree. It argues that the definition implies that knowledge, for Locke, is propositional, factive, requires belief or high confidence in the content known, and infallible. Finally, it suggests a way of reconciling Locke’s claims that all knowledge is certain and that some kinds of knowledge are more certain than others. The proposed solution is that Locke uses ‘certain’ and related terms in two ways. In one sense, being certain is an all-or-nothing affair. But in the other sense, certainty admits of degrees. In the former sense, all knowledge is certain, but in the latter sense, some kinds of knowledge have higher degrees of certainty than others.