Philosophy of the past three centuries is concerned basically with two questions: which world are we in?—and, who the devil are we? These questions arise in the following way. Traditional societies possess reasonably rounded-off and selfmaintaining world-pictures. But the advancement of learning and the broadening of horizons have dealt these pictures some devastating blows. So rival worlds, most of them sound by their own lights, make their mutually incompatible claims on our belief, our cognitive loyalty. Though one may temporize, one must also choose: after all, we must needs be some place, and our various decisions must be taken against some background picture.