抄録
In the paper, I attempt to attain to a fundamental understanding of Plato's Idea of Good. For that purpose we must trace the process which led him to build up his thought of the Idea of Good. The original type of Plato's Idea of Good appears as πρωτον φιλον(=αγαθον) in Lysis, which in Phaedo reappears in the guise of το αγαθον και δεον(99C5). I find the "ου ενεκα"-ness of αγαθον revealed in πρωτον φιλον and the "δεον"-ness of αγαθον in το γαθον και δεον. I believe that the Idea of Good has these two moments of αγαθον, and that this recognition will offer much help to our further inquiry into Plato's Idea of Good.
