The labor of the past years being completed, when our inclination urged us to undertake something more worthy, and many illustrious matters presented themselves in the memory of sacred things, in which labor might be nobly bestowed, it was the very counsels and exhortations of friends that impelled us to apply our mind above all to the history of the Manichaeans.
For since, for the benefit of the ecclesiastical and Christian commonwealth, many most illustrious men, most eminent in learning, have written now one, now another history of the heretics — in which there shine forth more brightly than light the authority of the sacred pastors, the strength of their spirit, and the excellence of their office in harrying and refuting these men — I was led to the opinion that I should do a thing pleasing to readers and to the students of the best criticism, if I turned my counsel and labor to undertaking this task. Nor indeed was it hidden from me that much concerning this heresy is to be found scattered here and there in the writings of others;
which, if they were at some time weighed and reduced to the standards of truth, and drawn together as into one body, the reader's mind would easily emerge free from so many and such great annoyances, which it is now compelled to undergo — both in unrolling the volumes of many writers, and on account of various matters undigested and entangled with many difficulties, such as are wont to be met with in this kind of disputing and writing, and which above all torment the wits and have been accustomed to draw them most easily into errors. I was likewise not unaware that the non-Catholic man J. Beausobre had written, in the French tongue, a history of the Manichaeans consonant rather with his own party than with the truth, which he afterward
published in 1734 from the press of Frederick Bernard at Amsterdam, adorned with many notes. But what things, and how great, this author dared to devise for the hatred and ruin of the Catholic faith, can scarcely — indeed hardly — be set forth by anyone, since he directed his censorious pen especially against the ancient holy Fathers, against the pontiffs of the Roman See, and against the sacred synods convened on the occasion of this heresy; so as, forsooth, to carp at and utterly overthrow their manner of writing and speaking and their economy of acting by false annotations, or at least to twist them into a depraved meaning.
Wherefore even at the threshold of this work it behooved me to observe that I would entangle my mind in troublesome and laborious enough contentions, if I resolved to reject these Beausobrian books — which I was able to have in hand only late, and after I had written seventeen chapters of this history — and to dissolve their errors. But when, in running through the books of this non-Catholic man, I had met with innumerable things which were repugnant both to truth and to my own observations, I therefore strove to reduce what I had long since written to another method and manner of disputing, lest I should seem to have discoursed on the Manichaean matters as it were meagerly and thinly.
Therefore, whenever time could remain to me from the daily exercises of study and from the other duties to which I must give my effort, whether within the cloister or outside it, my purpose was not to waste good leisure in slothfulness and idleness; but I pondered with myself those things which might be conferred toward the common good and the benefit of letters, and toward the writing of ecclesiastical history. I therefore resolved to treat as truthfully as possible of the whole history of the Manichaeans. In composing which little books, I profess that I will cling to no partial biases from which the mind of a writer ought to be wholly estranged, since I have set before myself that truth alone is to be followed and defended by me to the best of my powers in these and the subsequent contentions.