The arguments by which he disparaged justice are mentioned by Lucius Furius in Cicero; I suppose, since he was discussing the Commonwealth, in order to introduce a defence and panegyric of that quality without which he did not think a commonwealth could be administered.
But Carneades, in order to refute Aristotle and Plato, the advocates of justice, collected in his first argument everything that was in the habit of being advanced on behalf of justice, in order afterward to be able to overturn it, as he did.
VII.

Many philosophers indeed, and especially Plato and Aristotle, have spoken a great deal of justice, inculcating that virtue, and extolling it with the highest praise, as giving to every one what belongs to him, as preserving equity in all things, and urging that while the other virtues are, as it were, silent and shut up, justice is the only one which is not absorbed in considerations of self-interest, and which is not secret, but finds its whole field for exercise out-of-doors, and is desirous of doing good and serving as many people as possible; as if, forsooth, justice ought to exist in judges only, and in men invested with a certain authority, and not in every one! But there is no one, not even a man of the lowest class, or a beggar, who is destitute of opportunities of displaying justice.

But because these philosophers knew not what its essence was, or whence it proceeded, or what its employment was, they attributed that first of all virtues, which is the common good of all men, to a few only, and asserted that it aimed at no advantage of its own, but was anxious only for that of others.

So it was well that Carneades, a man of the greatest genius and acuteness, refuted their assertions, and overthrew that justice which had no firm foundation; not because he thought justice itself deserving of blame, but in order to show that those its defenders had brought forward no trustworthy or strong arguments in its behalf.
Justice looks out-of-doors, and is prominent and conspicuous in its whole essence.
Which virtue, beyond all others, wholly devotes and dedicates itself to the advantage of others.
VIII.

* * * Both to discover and maintain.