civilization is in a continuous process of transformation. To philosophical systems, other philosophical systems succeed; to the social, pohtical, and economic needs of a particular period other needs succeed. These systems and needs repeat themselves, with alternating authority, in the course of the centuries, provoking that slow, tortuous movement in a generally upward direction which we call progress. In this upward movement Christianity ought to be the centripetal force, spurring on and leading forward humanity in the course of the various stages of its evolution, penetrating with its spirit and moulding with its Divine forms the manifestations peculiar to each of them, yet not wholly identifying itself with any of them. And he who regards as definite forms of Christianity what are only expressions peculiar to the civilization which at a given moment it has made its own, is inevitably co-operating towards its ruin.