The design of the following verses is: (1) to show HOW men came to be in the condition of sin, depravity, and inability and (2) to compare the two heads–Adam and Christ. God sees ALL MEN IN ADAM, their head and representative. In His descendants, we are under sin, condemnation, and death. God sees THE BELIEVER IN CHRIST, his head and representative. In Christ we are redeemed and we live in Him. In Adam we died; in Christ we live! In Adam we lost the way, the truth, and the life; Christ IS the way, the truth, and the life.
Adam is a type (in reverse) of Christ. The only way that Adam typified Christ was as the head of a race. The remainder of the comparison is the opposite (I Cor. 15:45-49).
The First Adams (man)(Vs. 12) By Adam's transgression sin entered this world. By representation and imputation, sin and its results (spiritual death, physical death, darkness, disease, and enmity against God) entered into all men. When Adam sinned and fell, we all sinned and fell. Sin was not only imputed to us but a nature of sin was imparted to us (Psalm51:5; Psalm 58:3).
We must go to to Verse 28 if we keep to the train of thought, for Verses 13-17 are in parenthesis to explain what he means by "for ALL sinned."
(Vs. 18) Therefore, as one man's (Adam's sin lead to judgment and condemnation for all whom he represented, so one man's (Christ's ) obedience and sacrifice brought justification, redemption, and life to all whom He represented. We were not present physically when Adam fell, but we were in his loins; and we were in him as the covenant head of the human race, therefore condemned. In the same fashion, when our Lord perfectly obeyed God's holy requirements and satisfied God's justice on the crosss, we were in Him as His seed and covenant people (I Cor. 15:21-22), and therefore accepted as justified.
(Vs. 19) The words "were made" and "be made" in this verse are important. Adam's sin did not put us on trial and make us only susceptible to sin nor lead us into sin, but by his fall we were actually MADE SINNERS. Even so Christ's obedience did not render us saveable nor enable us to be righteous before God by our own works, but we were made righteous and sanctified entirely on the basis of what He did (II Cor. 5:21).
(Vs. 20) Then the Law came in to make apparent the evil that was in us by birth and nature (Rom. 3:19-20; Rom. 7:7). The Law takes away all excuses and reveals to us what we are–guilty sinners! But where sin overflowed, abounded, and contaminated every faculty, the grace of God in Christ did much more overflow in justification (Col. 1:21-22), in regeneration (Rom. 8:1), and in sanctification (II Cor. 5:17).
(Vs. 21) Sin has such power over men in their state of nature that it is said to REIGN in death. It has dominion (controlling and commanding power) over voluntary subjects. So in a state of regeneration and righteousness in Christ the grace of God reigns and holiness becomes the governing principle (I John 5:3-5; Rom. 6:12-14).
Back to Verse 13.(Vs. 13-14) Verse 12 declares, "death passed upon all men." None can stop it or escape its power, because in Adam all sinned. Even those who lived before the Law was given at Sinai were sinners under condemnation. But someone will argue, "Where there is no Law, a man is not accountable." If this be true then why did death reign? Why did people die (even infants) who did not commit an act of rebellion like Adam? Adam was a figure of Christ in one respect, as we have stated (I Cor. 15:21-22).
(Vs. 15) Though in one sense Adam is a type of Christ, the fall in Adam and the judgment which followed are not worthy to be compared to the grace of God and the free gift of life which we have in Christ. In Adam we LOST ALL THINGS; in Christ we GAINED MUCH MORE than we lost.
(Vs. 16) The effect of Christ's obedience is not to be compared to the effect of Adam's sin.
Christ confers much more than we lost in the fall.
Christ pardons no one sin, but all sins.
Christ Justifies in such a way that the believer is righteous and can never perish (John 10:27-28).
(Vs. 17) If through Adam death reigned over us, MUCH MORE shall those who are made righteous by Christ reign with Him (Rom. 8:16-17).