[ULPIANUS libro II institutionum. ] §1.3.41.prTotum autem ius constitit aut in adquirendo aut in conseruando aut in minuendo: aut enim hoc agitur quemadmodum quid cuiusque fiat, aut quemadmodum quis rem uel ius suum conseruet, aut quomodo alienet aut amittat.
[ULPIANUS, Institutes, book 2] But the whole of law consists either in acquiring, or in preserving, or in diminishing: for either this is dealt with, namely, how something becomes the property of someone, or how someone preserves their property or right, or how they alienate or lose it.