"If forgers and malefactors are put to death by the secular power, there is much more reason for excommunicating and even putting to death one convicted of heresy"

Thomas Aquinas is suggesting that those who are convicted of heresy must be excommunicated and even put to death. He thinks that if the secular power is penalizing forgers and malefactors with death, then those who are founded guilty of heresy needs to be penalized even more severely. Aquinas is making the argument that heresy is a more severe crime than forgery and malefaction, and ought to be treated as such. He thinks that excommunication and even death are proper punishments for those convicted of heresy. Aquinas is making the point that heresy is a criminal activity that ought to not be ignored, which those who are convicted of it should be penalized accordingly. He is recommending that the secular power should take a tough position against heresy and those who are convicted of it must be held responsible for their actions.