Epistemic logic

Abstract

Knowledge has been subject of philosophical study since ancient times. This is not surprising since knowledge is crucial to humans in order to control their actions and the appetite for acquiring it seems innate to the human race. Phi- losophy, therefore, has always occupied itself with the question as to the nature of knowledge. This area of philosophy is generally referred to as epistemology from the Greek word for knowledge, viz. episteme. Plato defined knowledge as "justified true belief", and this definition has influenced philosophers ever since (cf. [6, 25]); for instance, it is still held by the contemporary philosopher Al- fred Ayer. Although sensible, this definition does not yet explain the nature of knowledge, since all of the three notions of `justification', `truth' and `belief' are not yet clear and still subject to discussion