the very permanence of marriage is destructive of those fleeting infatuations, which are born with the moment and die with it; it destroys selfishness, furthermore, because the mutual love of husband and wife takes them out of themselves into the incarnation of their mutual love, their other selves, their children; and finally it narrows selfishness because the rearing of children demands sacrifice, without which, like unwatered flowers, they wilt and die.