In this passage, Paul explains the doctrines of original sin, federal headship, imputed sin, and imputed righteousness. The basic idea of this passage is that, as Adam was the representative of all people, so Christ is the representative of all of His people. Therefore, the way in which God dealt with Adam is the way in which He deals with those who are represented by him, and the way in which God dealt with Christ is the way in which He deals with His people.
Paul begins with the word, “therefore,” indicating that he is about to explain how Christians have been reconciled to God through Christ. He next draws a comparison between the consequences of Adam’s life, and the consequences of Christ’s life. The first comparison begins with the fact that sin entered into the world through Adam’s sin, and death into the world through that sin. However, all men became sinners and died when Adam sinned, as verses 13-14 teach. In verse 13, Paul states that sin was in the world before the Law came, but sin is not imputed, or credited, when there is no law at all. The implication is that there was a law because sin was imputed to people. Paul gives more evidence for this in the next verse, where he says that death was in the world before Moses, or before the Law, and it had power over those who did not sin in the same way in which Adam sinned. An implication from this is that, because people who had not sinned like Adam did died, they must have died because of a sin that they did not personally commit. That sin was Adam’s sin. Therefore, when Paul says that all sinned, he means that all are treated as if they committed Adam’s sin. In other words, Adam sinned in the place of all of mankind. That is why all die.
In verse 14, Paul adds that Adam is a type, or symbol, of Him who was to come, or Christ, setting up the rest of his comparison between Adam and Christ. Next, he compares Christ’s gift to His people with Adam’s sin. He begins by saying that they are unlike each other. One reason for this is that God’s grace and gift was given in a greater measure than Adam’s sin gave death to people.
In verse 16, Paul presents another comparison between God’s gift and death. Again, he notes that they are unlike each other. They are unlike each other because judgment, or a verdict of guilty, arose from Adam’s sin, which led to death, but God’s gift arose from many sins, and led to justification. In other words, it only took one sin to lead to mankind’s damnation, but it did not matter how many sins were committed for justification to be given to men. In verse 17, Paul gives an implication of verse 16: if one man’s sin brought death to all men, then the life of those who receive God’s grace and gift will be greater than that death.
In verse 18, Paul begins his conclusion of this passage. One conclusion is that, just as mankind’s condemnation was the result of one sin, men’s justification was the result of one righteous act. The reasons for these realities include the fact that Adam’s sin made everyone a sinner, and that Christ’s righteousness will make His people righteous.
In verse 20, Paul brings up the Law again. He states that the purpose of the Law was to make the amount of sin in people’s lives increase. This was the result because people naturally disobey any law that is given to them by God. Therefore, when He increased the number of laws to obey, He increased the number of times that people could sin. However, His grace increased when sin increased so that His grace would have power over people, just as sin had power over people. The means of grace’s power was righteousness, and the end of it was eternal life. However, Christ is the One through whom grace reigns.