Everyone who sins also commits lawlessness. Sin is lawlessness.

 As Westcott has it: "Life reveals the children of God." There is no way of telling what a tree is other than by its fruits, and there is no way of telling what a man is other than by his conduct. John lays it down that any one who does not do righteousness is thereby demonstrated to be not of God. At present we shall omit the parenthesis and go straight on with the argument. 