Why do we become sinners?
We become sinners because we are born in sin as children of Adam, and the old Adamic nature rebels against God. The natural human tendency is to listen to the old Adam, so we sin. It is not ultimately because of what we have done, but because of what we are.
Les explains that people are not lost because they went out and got drunk one night, or because they cheated, stole, or committed immorality. They are lost because they are born in sin as children of Adam and have refused the remedy, which is the work of the cross. The old Adamic nature knows only one thing: to rebel against the things laid down by God Himself. The human natural tendency is to listen to the old Adam, and consequently we become sinners. It isn't because of what we've done; it's because of what we are. Paul constantly throws out that the cross has completed everything.