Gaius, a Roman lawyer of the 2nd century A.D., of whom next to nothing is known except his work, not even his family name. A decree of Valentinian declared him one of the five lawyers whose opinions were to have weight. His known works are the Institutes, Commentary on the Twelve Tables, the Edicts of Magistrates, and a work on the Lex Papia Poppaea. He was probably a practitioner of the conservative school, and much of his Institutes was incorporated in Justinian's Institutes, in much the same way that Blackstone's Commentary has been utilised by later writers. In 1816 Niebuhr discovered a palimpsest of his MSS. at Verona, and this has proved of great value for the light it throws upon antique procedure, and upon the way in which variation of the "formulae" constituted a kind of equitable system.