But there is no end to their subtilties. There are jurists who in this case would distinguish custom from prescription, so that if they are debarred from the one, they may fall back upon the other. But the distinction which they set up is most absurd. They say that the right of one person which is taken away from him is given to another by prescription;[127] but that when any right is given to any one in such a way that it is not taken away from any one else, then it is called custom. As if indeed the right of navigation, which is common to all, upon being usurped by some one to the exclusion of all others, would not necessarily when it became the property of one be lost to all! This error receives support from misinterpretation of what Paulus has to say about a private right of possession on the sea.[128] Accursius† said that such a right could be acquired by privilege or custom. But this addition which in no way agrees with the text of the jurist seems to be rather the interpretation of a mischievous guesser than of a faithful interpreter. The real meaning of the words of Paulus has been already explained. Besides, if more careful consideration had been given to the words of Ulpian[129] which almost immediately precede those of Paulus, a very different assertion would have been made. For Ulpian acknowledges that if any one is prohibited from fishing in front of - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - usurpatum;[130a] hoc est receptum consuetudine, sed nullo iure, ideoque iniuriarum actionem prohibito non denegandam. Contemnit igitur hunc morem, et usurpationem vocat, ut et inter Christianos Doctores Ambrosius.[131a] Et merito. Quid enim clarius quam non valere consuetudinem, quae iuri naturae, aut gentium ex adverso opponitur?[132a] Consuetudo enim species est iuris positivi, quod legi perpetuae obrogare non potest. Est autem lex illa perpetua ut Mare omnibus usu commune sit. Quod autem in praescriptione diximus, idem in consuetudine verum est, si quis eorum qui diversum tradiderunt sensus excutiat, non aliud reperturum, quam consuetudinem privilegio parari. Atqui adversus genus humanum concedendi privilegium nemo habet potestatem; quare inter diversas respublicas consuetudo ista vim non habet. Verum omnem hanc quaestionem diligentissime tractavit Vasquius,[133a] decus illud Hispaniae, cuius nec in explorando iure subtilitatem, nec in docendo libertatem umquam desideres. Is igitur posita thesi: ‘Loca publica et iure gentium communia praescribi non posse’, quam multis firmat auctoribus; exceptiones deinde subiungit ab Angelo et aliis confictas, quas supra retulimus. Haec autem examinaturus recte iudicat istarum rerum veritatem pendere a vera iuris, tam naturae quam gentium cognitione. Ius enim naturae cum a - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -