ABSTRACT
Questions about knowledge can be divided into four main, though overlapping, groups, concerning its nature, its types, what is known, and its origin. Knowledge clearly differs in its nature from purely psychological states like feeling sure, for in straightforward contexts the word ‘know’, like ‘realize’, ‘REFUTE’, and many other words, can only be used by a speaker who himself has certain beliefs on the matter in question. If I say ‘Smith knows (or, Smith does not know) that fairies exist’ I commit myself to their existence, which I do not if I say ‘Smith believes (feels sure, is sure)…’ Verbs like ‘know’ are sometimes called factive to express this feature. Knowing is usually thought to involve believing, though some say that it replaces belief, or that one can believe one thing while somehow knowing the opposite.
