How Could One Sin Infect the Entire World?

There are actually several ways to understand this:

First, we must understand how covenants work. When the Lord God (Gen. 2:4) placed Adam in the Garden of Eden, he made a covenant with him as the federal head and representative of all men (Gen. 2:15-17; Hos. 6:7). As the Westminster Shorter Catechism states:

QUESTION 16. Did all mankind fall in Adam's first transgression?

ANSWER: The covenant being made with Adam, not only for himself, but for his posterity; all mankind, descending from him by ordinary generation, sinned in him, and fell with him, in his first transgression.

God is in charge and he is sovereign (Is. 45:9; Dan. 4:28-37; Rom. 9:20-21; Rev. 19:16). His law and covenant reign supreme (Ps. 82:1; Rom. 13:1; Rev. 20:12). Original sin was a violation of the covenant and law of God. It infected not only mankind, but nature, the environment, the entire universe (Rom. 8:22). It is like a drop of poison in a glass of pure water. None of the water is fit to drink. God demands justice for such acts, and the sentence for such an act is death (Gen. 2:17; Rom. 3:23). Subsequent acts of sin deserve the same judgment.

Second, the Fall was more than just "a" sin. One sin began a series of events. Like a snowball rolling downhill, one event led to other events, even including the very crucifixion of Christ himself (Acts 2:23-24; 4:27-28).

Though every temporal example of the eternal is limited, think for a moment of a jar full of white marbles symbolizing a complete perfect creation (Gen. 1:31). Now picture one black marble symbolizing sin (Gen. 3) being placed into the middle, which represents centering sin on Adam who was the covenant head (Gen. 2:15-17) and under whom all creation (the white marbles) was subjected (Gen. 1:28). This act displaces all the other marbles around it. All the marbles are now in a different location than what they were originally. Their relationship to the other marbles in the jar has now changed; some have shifted to a new position, others have rotated somewhat, but there has been a change. This reflects the change from God's holy plan. This shifting and displacement against God's plan is sin. So, from this example one may see how one sin affects everything around it.

Side Note: Though limited, this example is significant. It shows that when we sin, it affects others - now and in the future. One sin on our part changes everything. Although God is sovereign and has even accounted for the sin of the world in his eternal plan (Acts 2:23-24; 4:27-28; Rom. 9:17), understanding the impact of just one sin should assist us with living more holy lives. While they cannot erase acts of sin, acts of righteousness (let's call them red marbles) can impact the world in a good way! What we do, how we do it, and the reason(s) why we do it have an impact upon everything.

Third, to deny the effects of the Fall by one man, the first man (Adam), would be to deny the effects of salvation through the second Adam, Jesus Christ (Rom. 5:12-19; 1 Cor. 15:45, 47). If the sin of one man was not passed upon all, then the life/death/resurrection of one man - Jesus Christ - could not have been passed onto the elect (Eph. 1:4-5, 11, etc.) and so absolutely no one could be saved!

Fourth, the effects of just one sin is total. The Bible teaches that all mankind is dead in trespasses and sin (Eph. 2:1). Sin corrupts our whole person - mind and body. It severs our relationship with God. As we walk through this life in our decomposing "bodies of death" (Rom. 7:24), we infect everything. Here an example of Roman torture may be helpful. They would tie a dead body to a perfectly healthy one, thus allowing the decay and bacteria of the decomposing body to infect the living one. It was a slow and horrible death. As we are all tied to our father Adam, what a horrible death he spread to the whole human race! What a horrible death we live! The gangrene of death permeates all.

As Paul asks in Romans 7:24, "Who will rescue me from this body that is subject to death?" What is the answer? What is the only solution? Paul answers in Romans 7:25 saying, "Thanks be to God, who delivers me through Jesus Christ our Lord!"

Isn't it time to begin infecting other people's lives and our own (which must come first) for good instead of living out an infectious, gangrenous death which kills, steals, and destroys?