Now, there are three kinds of virtue, by means of which the possession of the kingdom of heaven is secured. The first is chastity, the second, contempt of the world, and the third, righteousness, which, as when joined together, they very greatly benefit their possessors, so, when separated, they can hardly be of any advantage, since every one of them is required, not for its own sake only, but for the sake of another. First of all, then, chastity is demanded, that contempt of the world may more easily follow, because the world can be more easily despised by those who are not held fast in the bonds of matrimony. Contempt of the world, again, is required, in order that righteousness may be maintained, which those can with difficulty fully preserve who are involved in desires after worldly advantages, and in the pursuit of mundane pleasures. Whosoever, therefore, possesses the first kind of virtue, chastity, but does not, at the same time, have the second, which is contempt of the world, possesses the first almost to no purpose, since he does not have the second, for the sake of which the first was required. And if any one possesses the first and second, but is destitute of the third which is righteousness, he labors in vain, since the former two are principally required for the sake of the third. For what profits it to possess chastity in order to contempt of the world, and yet not to have that on account of which you have the other? Or why should you despise the things of the world, if you do not observe righteousness, for the sake of which it is fitting that you should possess chastity, as well as contempt for the world? For as the first kind of virtue is on account of the second, and the second on account of the third, so the first and the second are on account of the third; and if it does not exist, neither the first nor the second will prove of any advantage.