Romans 5:19 For as through the one man's disobedience the many were made sinners, even so through the obedience of the One the many will be made righteous. According to a Calvinist not all were made sinners because in the contrast between the many and the one, the many does not refer to everyone but the one.
This particular part of Scripture deserves its own thread. What I am about to say is not going to be comprehensive. Adam is the old Federal head in that because of his sin all stand condemned. Christ is the Federal Head for all who are in Him.
In verse 15 of this chapter it says that many died through the transgression of the one man. That "one man" is Adam. All didn't die because Elijah and Enoch did not experience death.
Continuing in verse 15 :" how much more did the grace of God and the gift by the grace of the one man Jesus Christ multiply to the many!"
The 'many' are the ones in Him; that's the elect Church --His body. The redemption of Christ is applied to them. Those in Christ are considered righteous and vindicated because of what their Federal Head has accomplished for them. So then, there is the doctrine of imputation. Adam's sin has been imputed to the human race. In contrast, Christ the new Federal Head has imputed his righteousness to the many who are under his rule. Adam represented the entire human race. Christ represented those in Him.
Verse 18 :" Consequently, just as the trespass resulted in condemnation for all people, so also one righteous act resulted in justification and life for all people."
Obviously all people are not justified and have eternal life. In Romans 8, within what's called The Golden Chain, there is verse 30 :"And those he predestined, he also called; those he called, he also justified, he also glorified."
And
those, not every human being.
Verse 19 : "For just as through the disobedience of the one man the many were made sinners, so also through the obedience of the one man the many will be be made righteous."
The words
the many in the first clause means the mass of mankind.
The many in the last clause means that part of humanity who will be made righteous