The broadest definition of the term intuition is "immediate apprehension." Apprehension is used to cover such disparate states as sensation, knowledge, and mystical rapport. Immediate has as many senses as there are kinds of mediation: It may be used to signify the absence of inference, the absence of causes, the absence of the ability to define a term, the absence of justification, the absence of symbols, or the absence of thought. Given this range of uses, nothing can be said about intuition in general. Instead, it is necessary to pick out those principal meanings of the term that have played the most important roles in philosophical controversy and to discuss each of these individually.

Four principal meanings of intuition may be distinguished: (1) Intuition as unjustified true belief not preceded by inference; in this (the commonest) sense "an intuition" means "a hunch." The existence of hunches is uncontroversial and...