What is Sin?

When Paul describes the sins of his own people in Romans 2:24, the climax of the indictment is this: "The name of God is blasphemed among the Gentiles because of you."

What makes sin, sin, is not first that it hurts people, but that it blasphemes God. This is the ultimate evil and the ultimate outrage in the universe.

The glory of God is not honored.
The holiness of God is not reverenced.
The greatness of God is not admired.
The power of God is not praised.
The truth of God is not sought.
The wisdom of God is not esteemed.
The beauty of God is not treasured.
The goodness of God is not savored.
The faithfulness of God is not trusted.
The promises of God are not relied upon.
The commandments of God are not obeyed.
The justice of God is not respected.
The wrath of God is not feared.
The grace of God is not cherished.
The presence of God is not prized.
The person of God is not loved.

The infinite, all-glorious Creator of the universe, by whom and for whom all things exist (Rom. 11:36) - who holds every person's life in being at every moment (Acts 17:25) - is disregarded, disbelieved, disobeyed, and dishonored by everybody in the world. That is the ultimate outrage of the universe.

John Piper - The Greatest Thing in the World