Herein also Luther found the theology of St. Augustine in accord with the testimony of the great Apostle. While studying that theology, his conviction of the power of sin and the powerlessness of man's own strength to overcome it, grew more and more decided. But St. Paul taught him to understand that belief somewhat differently to St. Augustine. To Luther it was not merely a recognition of objective truths or historical facts. What he understood by it, with a clearness and decision which are wanting in St. Augustine's teaching, was the trusting of the heart in the mercy offered by the message of salvation, the personal confidence in the Saviour Christ and in that which He has gained for us. With this faith, then, and by the merits and mediation of the Saviour in whom this faith is placed, we stand before God, we have already the assurance of being known by God and of being saved, and we are partakers of the Holy Spirit, who sanctifies more and more the inner man. According to St. Augustine, on the contrary, and to all Catholic theologians who followed his teaching, what will help us before God is rather that inward righteousness which God Himself gives to man by His Holy Spirit and the workings of His grace, or, as the expression was, the righteousness infused by God. The good, therefore, already existing in a Christian is so highly esteemed that he can thereby gain merit before the just God and even do more than is required of him. But to a conscience like Luther's, which applied so severe a standard to human virtue and works, and took such stern count of past and present sins, such a doctrine could bring no assurance of forgiveness, mercy, and salvation. It was in faith alone that Luther had found this assurance, and for it he needed no merits of his own. The happy spirit of the child of God, by its own free impulse, would produce in a Christian the genuine good fruit pleasing in God's sight. It was a long time before Luther himself became aware how he differed on this point from his chief teacher amongst theologians. But we see the difference appear at the very root and beginning of his new doctrine of salvation; and it comes out finally, based on apostolic authority, clear and sharp, in the theology of the Reformer.