Sin began with Satan’s rebellion and entered mankind through Adam’s disobedience, bringing death; Jehovah is not its source, and Christ is its remedy.
Explaining the Concept of Sin to Someone Who Does Not Believe in Absolute Morality: A Biblical and Rational Evangelistic Approach
How do you explain sin to someone who denies absolute morality? Appeal to their conscience, expose moral inconsistency, and present the biblical truth.

