Especially in antiquity, rivers would both consist of a great resource, and they would exert a fearsome destructive power—vis cui resisti non potest, as Roman jurists used to assert. To prevent the risk of floods, Romans would not only carry out important public works, but also establish technical-juridical rules to induce both private individuals and communities to take care of the problem. Those rules were partly drawn up in public documents (such as praetorian edicta, leges dictae and so on), partly conceived by Roman jurists in a continuous debate starting at least from the first century AD to the third century AD and partly developed by discussions among Roman land surveyors.

In a well-known fragment of Justinian's Digest, Ulpian addresses the students who are about to face the world of law by reading his Institutes: the young people who are going to dedicate themselves to the law must know that it derives and is founded on justice and this because -according to the elegant definition of Celsus -it is indeed an ars, but an ars that deals with the ultimate goal of all research, that is, good and equity. Jurists are sometimes called sacerdotes of this ars -Ulpian continuesand rightly so: in fact they cultivate justice and bring news of the good and the fair by separating the fair from the iniquitous and the licit from the illicit, anxious to form good people not because of the fear of punishment but because of the encouragement derived from the awards, and aspiring to the real philosophy, not to the simulated one. The text has been studied a lot by Roman law scholars, but this essay offers some further interpretative clues concerning, in particular, the last expression of the fragment, namely that jurists tend -nisi fallor, the jurist controversially adds -to the true philosophy, not to the simulated one.