As the _third_ book of Cicero’s treatise began a second day’s colloquy, it was doubtless furnished with a proœmium, the greater part of which is now lost, as also a considerable portion of the commencement of the dialogue. Towards the conclusion of the preceding book, Scipio had touched on the subject, how far the observance of justice is useful to a state, and Philus had proposed that this topic should be treated more fully, as an opinion was prevalent, that policy occasionally required injustice. Previously to the discovery of Mai, we knew from St Augustine, _De Civitate Dei_, that in the third book of the treatise _De Republicâ_, Philus, as a disputant, undertook the cause of injustice, and was answered by Lælius. In the fragment of the third book, Philus excuses himself from becoming (so to speak) the devil’s advocate; but at length agrees to offer, not his own arguments on the subject, but those of Carneades, who, some years before, had one day pleaded the cause of justice at Rome, and next day overturning his own arguments, became the patron of injustice. Philus accordingly proceeds to contend, that if justice were something real, it would be everywhere the same, whereas, in one nation, that is reckoned equitable and holy, which in another is unjust and impious; and, in like manner, in the same city, what is just at one period, becomes unjust at another. In the palimpsest, these sophisms, which have been revived in modern times by Mandeville and others, are interrupted by frequent chasms in the MS. Lælius, as we learn from St Augustine, and from a passage in Aulus Gellius, was requested by all present to undertake the defence of justice; but his discourse, with the exception of a few sentences, is wholly wanting in the palimpsest. At the close he is highly complimented by Scipio, but a large _hiatus_ again intervenes. After this, Scipio is found contending, that wealth and power, Phidian statues, or the most magnificent public works, do not constitute a republic, but the _res populi_, the good of the whole, and not of any single governing portion of the state. He then concludes with affirming, that of all forms of government, the purely democratic is the worst, and next to that, an unmixed aristocracy.