Reliabilism

Reliabilism is an approach to the nature of knowledge and of justified belief. Reliabilism about justification, in its simplest form, says that a belief is justified if and only if it is produced by a reliable psychological process, meaning a process that produces a high proportion of true beliefs. A justified belief may itself be false, but its mode of acquisition (or the way it is subsequently sustained) must be of a kind that typically yields truths. Since random guessing, for example, does not systematically yield truths, beliefs acquired by guesswork are not justified. By contrast, identifying middle-sized physical objects by visual observation is presumably pretty reliable, so beliefs produced in this manner are justified. Reliabilism does not require that the possessor of a justified belief should know that it was reliably produced. Knowledge of reliability is necessary for knowing that a belief is justified, but the belief can be justified without the agent knowing that it is.

A similar reliabilist account is offered for knowledge, except that two further conditions are added. First, the target belief must be true and, second, its mode of acquisition must rule out all serious or ‘relevant’ alternatives in which the belief would be false. Even an accurate visual identification of Judy does not constitute knowledge unless it is acute enough to exclude the possibility that it is her twin sister Trudy instead.

One major virtue of reliabilism is its ability to secure knowledge against threats of scepticism. In place of excessive requirements often proposed by sceptics, reliabilism substitutes more moderate conditions. People do not need infallible or certainty-producing processes to have justified beliefs, according to reliabilism, only fairly reliable ones. Processes need not exclude radical alternatives like Descartes’ evil demon in order to generate knowledge; they need only exclude realistic possibilities like the presence of an identical twin.