Obbligazioni naturali e diritto comune. Un problema metodologico per il monismo giuridico.

Natural obligations are defined by modern civil Codes as the impossibility of requiring a performance not due, but spontaneously paid, when that performance has its ground in a moral duty. This conception was formed in fairly recent times, as opposed to the conception of naturalis obligatio proper to the ius commune, the legal system born in the Middle Ages and hegemonic in continental Europe until the French Revolution. The essay outlines the key moments of this doctrine, highlighting a paradox: the Civil Codes construct their own model of natural obligation against a "Roman model" that has nothing to do with the law of ancient Rome, but is constructed by medieval jurists.