The Confusion Over Justification in Church History
We now know that our current New Calvinists were (are) not the first in church history to have confounded justification and sanctification. Their error is from long, long ago.
"The doctrine of justification was not always clearly understood.
Some of the earliest church fathers already speak of justification by faith, but it is quite evident that they had no clear understanding of it and of its relation to faith. Moreover, they did not sharply distinguish between regeneration and justification. A rather common misrepresentation was that regeneration takes place in baptism and includes the forgiveness of sins. Even Augustine does not seem to have had an accurate understanding of justification as a legal act, as distinguished from the moral process of sanctification, though it is quite evident from the whole tenor of his teachings and also from separate statements, that he regarded the grace of god in the redemption of sinners as free, sovereign, and efficacious, and in no way dependent on any merits of men.
The confounding of justification and sanctification continued into the Middle Ages and gradually acquired a more positive and doctrinal aspect. According to the prevailing teachings of the Scholastics, justification includes two elements: man’s sins are forgiven, and he is made just or righteous. There was a difference of opinion as to the logical order of these two elements, some reversing the order just indicated. This was also done by Thomas Aquinas, and his view became the prevalent one in the Roman Catholic church. grace is infused in man, whereby he is made just, and partly on the basis of this infused grace, his sins are pardoned. This was already an approach to the evil doctrine of merit, which was gradually developed in the middle Ages in connection with the doctrine of justification. The idea found favor ever-increasingly that man is justified in part on the basis of his own good works. The confounding of justification and sanctification also led to divergent opinions on another point. Some of the Scholastics speak of justification as an instantaneous act of God, while others describe it as a process. In the Canons and Decrees of the Council of Trent we find the following in Chapt. XVI, Canon IX: “If anyone saith, that by faith alone the impious is justified in such wise as to mean, that nothing else is required to co-operate in order to the obtaining of the grace of justification, and that it is not in any way necessary, that he be prepared and disposed by the movement of his own will: let him be anathema. And Canon XXIV speaks of an increase in justification and therefore conceives of it as a process: “If any one saith, that the justice received is not preserved and also increased before God through good works; but that the said works are merely the fruits and signs of justification obtained, but not a cause of the increase thereof: let him be anathema.”
– Louis Berkhof, Systematic Theology, pp. 511-512