The chief goal of this book is to fight for the Catholic Church, as a son for the honor of his mother, against those who teach the impunity of heretics, and defend it so that it may shown that she has decreed nothing unjust, and she has decreed nothing which is unbecoming a true mother. No one ever has discussed this subject. For even though many Catholic theologians and learned men have written against those men who teach the impunity of heretics, who argue with many and very evident reasons, in favor of the punishment of heretics, that the punishment of heretics is very just, yet none of them has proved that all those punishments, which were decreed by canon and civil law against heretics are just: nor about this matter did any of them ever discuss.

This work is divided into three books. In the first book is discussed about heresies themselves, where it is shown, who they are, and how they ought to be correctly admonished about their heresies, so that if perhaps having acknowledged their error they would want to return to the path of truth, by what benignity and mercy they ought to be received by the Church. Next in the second book it is treated regarding those heretics, who hold so firmly onto their heresies, that they nowise can be torn away from them: one by one the punishments are enumerated, which have been decreed for them by law, which after having been accurately presented, and it is proved herein that they all are very justly inflicted for many and very evident reasons. Finally in the third book some ways are shown by which one can prevent heresies, lest any heretics thereafter arise among Christians, whom the prelates of the Church and rulers of the world cannot leave unpunished without the ignominy of laxity and slothfulness.