...paved with good intentions

Yet the inquisitor was frequently baffled in this intellectual digladiation by the innocence or astuteness of the accused. His resources, however, were by no means exhausted, and here we approach one of the darkest and most repulsive aspects of our theme. Human inconsistency, in its manifold development, has never exhibited itself in more deplorable fashion than in the instructions on this subject transmitted to their younger brethren by the veterans of the Holy Office— instructions intended for none but official eyes, and therefore framed with the utmost unreserve...Yet through all this there shines the evident conviction that they are doing the work of God. No labor is too great if they can win a soul from perdition; no toil too repulsive if they can bring a fellow-creature to an acknowledgment of his wrong-doing and a genuine repentance that will wipe out his sins; no patience too prolonged if it will avoid the unjust conviction of the innocent. All the cunning fence between judge and culprit, all the fraud, all the torture of body and mind so ruthlessly employed to extort unwilling confessions, were not necessarily used for the mere purpose of securing a victim, for the inquisitor was taught to be as earnest with the recalcitrants against whom he had sufficient testimony as with the cases in which evidence was deficient. With the former he was seeking to save a soul from immolating itself in the pride of obstinacy; with the latter he was laboring to preserve the sheep by not liberating an infected one to spread pestilence among the flock. It mattered little to the victim what were the motives actuating his persecutor, for conscientious cruelty is apt to be more cold-blooded and calculating, more relentless and effective, than passionate wrath, but the impartial student must needs recognize that while many inquisitors were doubtless dullards who followed unthinkingly a prescribed routine as a vocation, and others were covetous or sanguinary tyrants actuated only by self-interest or ambition, yet among them were not a few who believed themselves to be discharging a high and holy duty, whether they abandoned the impenitent to the flames, or by methods of unspeakable baseness rescued from Satan a soul which he had reckoned as his own. They were instructed that it was better to let the guilty escape than to condemn the innocent, and, therefore, that they must have either clear proofs or confession. In the absence of absolute evidence, therefore, the very conscientiousness of the judge, under such a system, led him to resort to any means to satisfy himself by wringing an acknowledgment from his victim.

Henry Charles Lea. A History of the Inquisition of the Middle Ages; volume I (Kindle Locations 6879-6903). Kindle Edition.