Whereas Augustine taught that the sinner is made righteous in justification, Melanchthon taught that he is counted as righteous or pronounced to be righteous. For Augustine, 'justifying righteousness' is imparted; for Melanchthon, it is imputed in the sense of being declared or pronounced to be righteous. Melanchthon drew a sharp distinction between the event of being declared righteous and the process of being made righteous, designating the former 'justification' and the latter 'sanctification' or 'regeneration.' For Augustine, these were simply different aspects of the same thing . . . The importance of this development lies in the fact that it marks a complete break with the teaching of the church up to that point. From the time of Augustine onwards, justification had always been understood to refer to both the event of being declared righteous and the process of being made righteous. Melanchthon's concept of forensic justification diverged radically from this. As it was taken up by virtually all the major reformers subsequently, it came to represent a standard difference between Protestant and Roman Catholic from then on. In addition to differences regarding how the sinner was justified, there was now an additional disagreement on what the word 'justification' designated in the first place. The Council of Trent, the Roman Catholic church's definitive response to the Protestant challenge, reaffirmed the views of Augustine on the nature of justification, and censured the views of Melanchthon as woefully inadequate . . . the concept of forensic justification actually represents a development in Luther's thought . . . .
(Alister McGrath, Reformation Thought: An Introduction, 2nd ed., Grand Rapids, MI: Baker Book House, 1993, 108-109; emphasis in original)