That’s all we may expect of man, this side. The grave: his good is—knowing he is bad.

In this line Browning frames a bleak but morally pointed view of human nature: on “this side” of the grave, the highest realistic achievement is not purity but self-knowledge. The paradox—“his good is—knowing he is bad”—suggests that moral progress begins with honest recognition of one’s flaws, limits, and capacity for wrongdoing. The grave functions as a boundary marker: complete moral resolution or perfect justice is deferred beyond earthly life, so the attainable virtue here is humility and clear-sighted conscience. The statement also implies a critique of self-righteousness: the person who believes himself good may be more dangerous than the one who admits his moral frailty.