12 Therefore, just as sin came into the world through one man [Adam], and death through sin, and so death [both physical and spiritual] spread to all men because all sinned—
and so [by the sin of one man] death spread to all men
Since Adam’s sin involved his posterity in sin, death spread to all of humanity. Humanity sinned, not subsequently, but in the first man. The sin of one was the sin of all. Universal death is the consequence of universal sin in Adam.
The parallelism between Adam and Christ later in this chapter shows people are constituted sinners or righteous, not by their own personal sin, but by virtue of the sin of Adam or the forgiveness of Christ, as the case may be. The issue is the distinction between corporate and personal sin. Both condemnation and death are traced to Adam in verses 15-19.
Sin started with Adam, but that is not the point of this phrase. The idea is that sin came to every human being through one man. The contrast is Christ giving those who believe a righteous status before God resulting in eternal life.
Death came to all men from Adam’s sin; eternal life comes for some men from Christ.
This principle applies to indivisibility of merit. The merit of Christ’s righteousness is indivisible. God imputes the whole of His righteousness to every individual believer alike. We do not receive a part of His righteousness, but we receive the entirety of that righteousness by His declaring us as righteous as He is righteous. Each believer is 100% declared right before God. We all receive the total worthiness of what our Lord did on the cross. We do not receive a fractional part of it.
There are two imputations:
Actual: God imputes His justice on the principle of affinity. There is an affinity between Adam’s original sin and our sin capacity. There is no discontinuity between the two. The affinity is the agreement between the imputation of Adam’s original sin and the resulting sin capacity. That is actual imputation. There is no affinity or agreement of similarity between what God imputes and the recipient. This involves three actual imputations:
Adam’s original sin to the sin capacity
Eternal life to the human being
God’s righteousness imputed to the believer judicially
Judicial: There is no affinity in judicial imputation. There are two judicial imputations:
God imputes personal sin to Christ on the cross. Jesus did not have a sin capacity and never committed personal sin; there was nothing in Him that had any affinity to personal sin.
God imputes His righteousness to the believer at the point of salvation. There is nothing in man that has affinity with God’s righteousness. From the standpoint of his sin capacity, his personal sin, and the imputation of Adam’s original sin, man has no affinity with God. He has nothing worthy of salvation, so he needs a judicial imputation of God’s righteousness to his eternal account.