“The established laws are to be understood benignly, so as to preserve their spirit, and prevent their departure from equity; for the Judge recognizes ordainments as legitimate when they conform to the principles of justice (_ratio equitatis_).... Interpretation is sometimes general and imperative, as when the lawgiver declares it: then it must be applied not only to the matter for which it is announced, but in all like cases. Sometimes an interpretation is imperative, but only for the special case, like the interpretation which is declared by those adjudicating a cause. It is then to be accepted in that cause, but not in like instances; for not by precedents, but by the laws are matters to be adjusted. There is another kind of interpretation which binds no one, that made by teachers explaining an ambiguous law, for although it may be admissible because sound, still it compels no one. For every interpretation should so be made as not to depart from justice, and that all absurdity may be avoided and no door opened to fraud.”[387] One must suppose that such concise statements were explained and qualified in the author’s lectures. But even as they stand, they afford an exposition of Roman principles of interpretation. Not only under the Roman Empire, but subsequently in mediaeval times, the Roman lawyer or the canonist did not pay the deference to adjudicated precedent which is felt by the English or American judge. The passage in the _Codex_ which “Irnerius” was expounding commands that the judge, in deciding a case, shall follow the laws and the reasoning of the great jurists, rather than the decision of a like controversy. Since the author of this _Summa_ weighs the justice, the reason, and the convenience of the laws, and compares them with each other, his book is a work of jurisprudence. Its qualities may be observed in its discussion of _possession_ and the rights arising therefrom. The writer has just been expounding the _usucapio_, an institution of the _jus civile_ strictly speaking, whereby the law of Rome in certain instances protected and, after three years, perfected, the title to property which one had in good faith acquired from a vendor who was not the owner: