Lactantius — Divine Institutes 5.16

I have set out why the philosophers could neither find justice nor defend it: now I return to what I had aimed at. Carneades therefore, since what the philosophers asserted was weak, took boldness to refute, because he understood it could be refuted. The sum of his dispute was this: that humans sanctioned laws for themselves for utility, namely varied according to customs, and among the same people often changed according to times, but that there is no natural right; that all both humans and other animals are driven to their own advantages with nature leading; accordingly that justice is either nothing or, if there is any, it is the height of folly, since it would harm itself by consulting others' benefits. And he brought in these arguments: that for all peoples who flourished by empire and for the Romans themselves also, who possessed the whole world, if they should wish to be just, that is if they restore what is another's, they must return to huts and lie in want and miseries. Then leaving common matters he came to particular ones.

A good man, he says, if he has a runaway slave or an unhealthy and plague-ridden house, whose faults he alone knows, and therefore advertises them to sell, will he declare that he is selling a runaway slave or a plague-ridden house, or will he hide it from the buyer? If he declares, he will be judged good indeed, because he will not deceive, but still foolish, because he will either sell cheaply or not sell at all; if he hides, he will be wise indeed, because he will consult his interest, but the same man wicked, because he will deceive. Again if he finds someone who thinks he is selling brass, when it is gold, or lead, when it is silver, will he be silent, to buy it cheap, or will he point it out, to buy dear? It plainly seems foolish to prefer to buy dear. From which he wanted it understood both that he who is just and good is foolish and that he who is wise is wicked, and yet that it can happen without ruin that humans be content with poverty. He therefore crossed to greater matters, in which no one could be just without danger to life.

For he said: surely justice is not to kill a human, not to touch what is another's at all. What then will the just man do if by chance he has suffered shipwreck and someone weaker in strength has seized a plank? Will he not thrust that man from the plank, so that he himself may climb and escape by leaning on it, especially when there is no witness in mid-sea? If he is wise, he will do it: for he himself must perish unless he does it; but if he prefers to die rather than lay hands on another, then that man is just, but (the same) foolish, who does not spare his own life while he spares another's. Likewise if when his own battle-line is routed the enemies begin to pursue, and that just man has found someone wounded sitting on a horse, will he spare him, so that he himself may be killed, or throw him from the horse, so that he himself can flee the enemy? If he does it, he is wise, but the same wicked; if he does not, he must be just, but the same foolish. So then when he had divided justice into two parts, saying one is civic, the other natural, he overturned both, because that civic one is wisdom indeed, but is not justice, while that natural one is justice indeed, but is not wisdom. These things are plainly sharp and poisoned and such as Marcus Tullius could not refute. For when he makes Laelius answer Furius and speak for justice, he passed by these things unrefuted as if past a pit, so that the same Laelius seems to have defended not the natural justice, which had come under the charge of folly, but that civic justice, which Furius had granted was wisdom indeed, but unjust.