The Reformation focused on the question, How is a person justified? Clearly justification involves a legal judgment by God, a declaration by him that we are just. Then the burning question becomes this: On what basis or grounds does God ever declare anyone just? Must we first become just inherently before God will make such a declaration? Or does he declare us just before we are in ourselves actually just? John Calvin answered the question this way:
A man is said to be justified in the sight of God when in the judgment of God he is deemed righteous, and is accepted on account of his righteousness; for as iniquity is abominable to God, so neither can the sinner find grace in his sight, so far as he is and so long as he is regarded as a sinner. Hence, wherever sin is, there also are the wrath and vengeance of God. He, on the other hand, is justified who is regarded not as a sinner, but as righteous, and as such stands acquitted at the judgment seat of God, where all sinners are condemned…Thus we simply interpret justification, as the acceptance with which God receives us into his favour as we were righteous; and we say that this justification consists in the forgiveness of sins and the imputation of the righteousness of Christ.
– John Calvin
as quoted by Sproul, R.C.; Grace Unknown: The Heart of Reformed Theology; Baker Books; Grand Rapids, MI; copyright 1997; p. 60-61