Now, when we inquire into the reason of this powerful hold which Christianity has on so many men, we find it is because it meets certain inherent cravings of human nature. Some of these, such as man's belief in prayer, and his sense of responsibility, are of course satisfied by any form of Theism. So also is his idea of justice, which requires virtue and vice to be suitably rewarded hereafter, since they are not here. But man's nature has many other cravings besides these; yet Christianity seems to satisfy it everywhere. We will consider four points in detail and select _Sorrow_ and _Sin_, _Death_ and _Eternity_. The first three, and possibly the fourth, all have to be faced; they are the common heritage of all mankind. And while Rationalism does not help us to face any of them, and Natural Religion leaves much in uncertainty, Christianity meets the needs of mankind throughout, or at all events far better than any other religion. And first, as to _Sorrow_. It is indisputable that in this life man has to bear a great deal of sorrow and suffering; and it is also indisputable that when in sorrow he longs for someone who can both sympathise with him, and help him. An impersonal God can, of course, do neither; indeed, we might as well go for comfort to the force of gravity. And though a personal God can help us, we do not feel sure that He can sympathise with us. On the other hand, fellow-men can sympathise, but they cannot always help. In Christ alone we have a Being Who entirely satisfies human nature; for being Man, He can sympathise with human sorrow, and being God, He can alleviate it. So here Christianity supplies a universal want Of course, the doctrine of the _Incarnation_ also satisfies mankind in other respects, especially in presenting him with a worthy Being for his affections, and with a perfect Example; but these points have been already noticed in Chapter XIII. Next, as to _Sin_. Here again the facts are practically undisputed. Man's sense of sin is universal, so also is his belief in the justice of God; and therefore in all ages man has longed for some means of appeasing the Deity. The widespread custom of sacrifice is a conclusive proof of this. Yet, wherever Christianity has been accepted, such sacrifices have been abandoned. It is scarcely necessary to point out the reason for this. The Christian doctrine of the _Atonement_ entirely satisfies these cravings of mankind. It admits the fact of sin; it provides a sufficient Sacrifice for sin, which man could never provide for himself, and it thus assures him of complete forgiveness. Yet, as shown in Chapter XIII., it does all this without in any way lessening the guilt of sin, or allowing man to sin on with impunity; for it makes _repentance_ an essential condition of forgiveness.