The Idea: What sin is
Sin is acting in a way which violates God’s principle of right and wrong. We can sin by doing something which is wrong and we can sin by failing to do something which is right. The Bible gives three complementary statements about the nature of sin:
"Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness." (1 John 3:4)
"But whoever has doubts is condemned if he eats, because the eating is not from faith. For whatever does not proceed from faith is sin." (Romans 14:23)
"So whoever knows the right thing to do and fails to do it, for him it is sin." (James 4:17)
These explain sin as the violation of God’s law, or as actions that are not compatible with faith in God, or actions which we should do but don’t do. The point is that God has a principle of right and wrong which we should follow; when we fail to follow it we are committing sin.