The theory of knowledge. Its central questions include the origin of knowledge; the place of experience in generating knowledge, and the place of reason in doing so; the relationship between knowledge and certainty, and between knowledge and the impossibility of error; the possibility of universal scepticism; and the changing forms of knowledge that arise from new conceptualizations of the world. All of these issues link with other central concerns of philosophy, such as the nature of truth and the nature of experience and meaning. It is possible to see epistemology as dominated by two rival metaphors. One is that of a building or pyramid, built on foundations. In this conception it is the job of the philosopher to describe especially secure foundations, and to identify secure modes of construction, so that the resulting edifice can be shown to be sound. This metaphor favours some idea of the ‘given’ as a basis of knowledge, and of a rationally defensible theory of confirmation and inference as a method of construction (see also foundationalism, myth of the given, protocol statements). The other metaphor is that of a boat or fuselage, that has no foundations but owes its strength to the stability given by its interlocking parts. This rejects the idea of a basis in the ‘given’, favours ideas of coherence and holism, but finds it harder to ward off scepticism.

The problem of defining knowledge in terms of true belief plus some favoured relation between the believer and the facts began with Plato’s view in the Theaetetus that knowledge is true belief plus a logos. For difficulties see Gettier examples. For further issues see confirmation theory, empiricism, feminism, naturalized epistemology, rationalism, relativism, reliabilism, social epistemology.