Justice is rather the activity of truth, than a virtue in itself. Truth tells us what is due to others, and justice renders that due. Injustice is acting a lie.

Walpole frames justice not as a standalone moral quality but as truth put into practice. On this view, truth is cognitive and declarative: it identifies what others are owed—rights, respect, fair treatment, or restitution. Justice is the corresponding action: delivering what truth has disclosed as due. The final sentence sharpens the ethical claim by redefining injustice as a kind of falsehood enacted in behavior—conduct that contradicts what one knows (or ought to know) to be true about others’ claims. The passage thus links moral wrongdoing to epistemic failure or bad faith: to be unjust is to live out a lie about other people’s standing and deserts.