God gave Adam a world full of good things to enjoy. He withheld one good thing from him, one tree, and called that tree the Tree of the Knowledge of Good and Evil. By withholding that one tree from Adam and making Adam’s very life contingent on not eating that tree, God taught Adam the heart of good and evil, which is that all good things come to us from God, for He is benevolent, but that all the things that God has given us must be enjoyed as God’s gifts to us and according to God’s command for their rightful use, for God is also sovereign.
When Adam ate of the tree, Adam denied that all things really did come from God. He believed the lie that the tree just existed of itself and could be used however Adam saw best. This is the lie that mankind is cursed to believe ever since, that God’s good creation simply exists of itself and that it is up to man to determine what it means and how it should be used.