In the study of Zen Buddhist Philosophy, Koan is found to be paradoxical and illogical, and is thus somewhat rationally unexplicable. The thesis shows ways to explain Koan and make it intellectually comprehensible. The thesis investigates how Koan has been employed by Zen masters and proposes logical ways to understand it. Even though Koan expresses itself in a paradoxical way, it has been shown that we may understand Koan by penetrating into the implications found in the Koan puzzles, rather than by attempting to understand their accounts directly. Three ways to understand the Koan riddles through their implications are presented: the implication of the aim of Koan; the implication of the absolute reality of Zen; and the implication of action. Although these ordinary methods are found to be useful in helping practitioners understand some Koan puzzles, the methods may not lead them to enlightenment, however.
