The simple answer to this is that we can neither dispense with Christianity nor put something in its place. We do not know (and it would be useless to wish to discover) what would have become of the civilized world, if Christianity had not appeared in it when it did; but it is certain that we can no longer get away from it now, nor ignore it, but we must reckon with it as with something that will endure, yet can not be wholly explained by science. True, science can not be prevented from discovering, as completely as possible, everything that is knowable, or from extending the sphere of the knowable as widely as possible; that is its right and its duty. With this there goes, in the conception of particular minds, the supposition that everything is knowable that concerns mankind, or that, at any rate, everything can be made knowable in time. This is the basis of a considerable part of the courage and the perseverance found in scientific investigation. But just as little may it be forbidden us to doubt that men will ever succeed in completely fathoming human nature in all its relationships to the universal Being and in its connection with all things; but even so, it is the duty (and of cultured people most of all) nevertheless, to stand firm, and in particular to put away the presumption with which imperfect knowledge, or even mere hypotheses, are wont to be set up in the place of the inward conviction as to the existence and worth of super-sensual things. Highly as humanity has cause to value science and its steady advance, it would, nevertheless, take a tremendous backward step, if one should be able to remove from the sphere of its life and from the motives of its actions everything that is not scientifically provable. This is the ideal of many educated people of our time, but it is a false and a very inadequate one. Our knowledge is patchwork, and will remain such. We shall scarcely ever be able to know even everything that concerns ourselves. Nor do the strongest motives of our best actions spring from the sphere of knowledge; otherwise the most learned people must always be the most perfect, which is by no means the case. Our spiritual Ego is rooted rather in the Unexplainable, and experience shows that if this something unexplainable is ever taken from the Ego in questions of faith, it tries to make up for the loss by adopting some superstition or other.