Everyone who sins also commits lawlessness. Sin is lawlessness.

 (ii) The passage must therefore mean this. Our hearts condemn us--that is inevitable. But God is greater than our hearts; he knows all things. Not only does he know our sins; he also knows our love, our longings, the nobility that never fully works itself out, our penitence; and the greatness of his knowledge gives him the sympathy which can understand and forgive. 