John Wesley on Romans 5:12

Therefore - This refers to all the preceding discourse; from which the apostle infers what follows. He does not therefore properly make a digression, but returns to speak again of sin and of righteousness. As by one man - Adam; who is mentioned, and not Eve, as being the representative of mankind. Sin entered into the world - Actual sin, and its consequence, a sinful nature. And death - With all its attendants. It entered into the world when it entered into being; for till then it did not exist. By sin - Therefore it could not enter before sin. Even so - Namely, by one man. In that - So the word is used also, 2Cor 5:4. All sinned - In Adam. These words assign the reason why death came upon all men; infants themselves not excepted, in that all sinned.