For assistance in auspication the magistrate summoned any person he pleased, who was rarely if ever a public augur.[606] An augur,[607] whether private or official, was a person who knew how to hold and to interpret auspices.[608] A college of public augurs[609] for the service of the state was established in the most primitive times. Probably comprising three members, one from each tribe, it was gradually increased till under Sulla it reached fifteen.[610] The members of the college were neither magistrates[611] nor prophets. They were rather the wise,[612] experienced[613] keepers and expounders of a sacred science and art[614]—the “interpreters of Jupiter All-Great and Good.”[615] Having to do with religion, they were sacerdotes, like the pontiffs, though not offerers of sacrifice (flamines).[616] The functions which they exercised independently of the magistrates included the inauguration of religious officials (inaugurare sacerdotes), the blessing of fields twice a year, and of the people after the close of a war.[617] In attending to such duties (auguria) only did they exercise their right to the auspices.[618] In a dependent though far more influential position they acted as the professionally skilled advisers and assistants of the magistrates in all matters of peace and war.[619] If a magistrate was not himself an augur,[620] it was of the utmost importance to have their service; for the science of discovering and interpreting the divine omens was intricate, mistakes were easy, and the slightest oversight might vitiate the whole business in hand. When in doubt as to the validity of the ceremony, either the magistrate to whom it belonged or the senate could refer the case to the college of augurs, which thereupon gave an opinion in the form of a decree. The senate then acted on the matter according to its judgment.[621] In case a law had been passed, a magistrate elected, or any public act performed against its wishes, it could inquire of the college of augurs whether the election or other act had been duly auspicated; and should a defect be alleged, the senate could annul the act or request the magistrate to resign. It required unusual courage in a man to keep himself in office in defiance of the authority of the senate and of the religious feeling of the whole people.[622] These considerations account for the great importance attaching to the presence of augurs in the comitia—a subject to be treated in another connection.[623]