With the development of the laws against heresy, and the organization of special tribunals for the application of those laws, it was soon perceived that an accusation of heresy was a peculiarly easy and efficient method of attacking a political enemy. No charge was easier to bring, none so difficult to disprove--in fact, from what we have seen of the procedure of the Inquisition, there was none in which acquittal was so absolutely impossible where the tribunal was desirous of condemnation. When employed politically the accused had the naked alternative of submission or of armed resistance. No crime, moreover, according to the accepted legal doctrines of the age, carried with it a penalty so severe for a potentate who was above all other laws. Besides, the procedure of the Inquisition required that when a suspected heretic was summoned to trial, his first step was humbly to swear to stand to the mandates of the Church, and perform whatever penance it should see fit to impose in case he failed to clear himself of the suspicion. Thus an immense advantage was gained over a political enemy by merely citing him to appear, when he was obliged either to submit himself in advance to any terms that might be dictated to him, or, by refusing to appear, expose himself to condemnation for contumacy with its tremendous temporal consequences.
It mattered little what were the grounds on which a charge of heresy was based. In the intricate intrigues and factional strife which seethed and boiled in every Italian city, there could be no lack of excuse for setting the machinery of the Inquisition in motion whenever there was an object to be attained. With the organization of the Hildebrandine theocracy the heretical character of simple disobedience, which had been implied rather than expressed, came to be distinctly formulated. Thomas Aquinas did not shrink from proving that resistance to the authority of the Roman Church was heretical. By embodying in the canon law the bull _Unam Sanctam_ the Church accepted the definition of Boniface VIII. that whoever resists the power lodged by God in the Church resists God, unless, like a Manichæan, he believes in two principles, which shows him to be a heretic. If the supreme spiritual power errs, it is to be judged of God alone; there is no earthly appeal. "We say, declare, define, and pronounce that it is necessary to salvation that every human creature be subjected to the Roman pontiff." Inquisitors, therefore, were fully justified in laying it down as an accepted principle of law that disobedience to any command of the Holy See was heresy; so was any attempt to deprive the Roman Church of any privilege which it saw fit to claim. As a corollary to this was the declaration that inquisitors had power to levy war against heretics and to give it the character of a crusade by granting all the indulgences offered for the succor of the Holy Land. Armed with such powers, it would be difficult to exaggerate the importance of the Inquisition as a political instrument.[204]