Actually the purest saint at the moment of his greatest strength is as weak as he was before his conversion. What has happened is that he has switched from his little human battery to the infinite power of God. He has quite literally exchanged weakness for strength, but the strength is not his; it flows into him from God as long as he abides in Christ. One of the heaviest problems in the Christian life is that of sanctification: how to become as pure as we know we ought to be and must be if we are to enjoy intimate communion with a holy God. The classic expression of this problem and its solution is found in Paul's epistle to the Romans, chapters seven and eight. The cry, "O wretched man that I am! who shall deliver me from the body of this death?" (7:24) receives the triumphant answer, "The law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death" (8:2). No one who has given attention to the facts will deny that it is altogether possible for a man to attain to a high degree of external morality if he sets his heart to it. Marcus Aurelius, the pagan emperor, for instance, lived a life of such exalted morality as to make most of us Christians ashamed, as did also the lowly slave Epictetus; but holiness was something of which they were totally ignorant. And it is holiness that the Christian heart yearns for above all else, and holiness the human heart can never capture by itself.