It may seem paradoxical to allocate eight centuries of philosophy, from the thirteenth to the twentieth centwy, to a single period. But this paradox merely throws into relief the difficulty of dividing Islamic philosophy into periods in a way that corresponds to what is customary in the history of philosophy. Let us begin by observing that if we go by the Islamic computation, this interval extends from the seventh centwy of the Hijrah to the end of the fourteenth centwy; and, further, that the sense of historical time and periods cannot be altogether the same when the thinker's inner life is centred and situated in relation to the era of the Hijrah, as when it is centred and situated in relation of the Christian era. Our own schema of Antiquity, Middle Ages and Modem Times has no corresponding basis in the time of the Islamic era. Of course, we can establish concordances between the calendars; but these concordances are entirely external and purely pragmatic, and bear no relation to real, existential contemporaneity. Our first problem, then, is the problem of a satisfactory division into periods.