Just because.
On the polyvalence of Scripture:
But here some one perhaps will ask, Since the canon of Scripture is complete, and sufficient of itself for everything, and more than sufficient, what need is there to join with it the authority of the Church’s interpretation? For this reason — because, owing to the depth of Holy Scripture, all do not accept it in one and the same sense, but one understands its words in one way, another in another; so that it seems to be capable of as many interpretations as there are interpreters. For Novatian expounds it one way, Sabellius another, Donatus another, Arius, Eunomius, Macedonius, another, Photinus, Apollinaris, Priscillian, another, Iovinian, Pelagius, Celestius, another, lastly, Nestorius another. Therefore, it is very necessary, on account of so great intricacies of such various error, that the rule for the right understanding of the prophets and apostles should be framed in accordance with the standard of Ecclesiastical and Catholic interpretation. (ch. 5)
Don’t preach heresy!
To preach any doctrine therefore to Catholic Christians other than what they have received never was lawful, never is lawful, never will be lawful: and to anathematize those who preach anything other than what has once been received, always was a duty, always is a duty, always will be a duty. (ch. 25)
Heresy is poison:
They have, in fact swallowed a quantity of poison — not enough to kill, yet more than can be got rid of; it neither causes death, nor suffers to live. O wretched condition! With what surging tempestuous cares are they tossed about! One while, the error being set in motion, they are hurried wherever the wind drives them; another, returning upon themselves like refluent waves, they are dashed back: one while, with rash presumption, they give their approval to what seems uncertain; another, with irrational fear, they are frightened out of their wits at what is certain, in doubt whither to go, whither to return, what to seek, what to shun, what to keep, what to throw away. (ch. 49)
They do, in fact, what nurses do when they would prepare some bitter draught for children; they smear the edge of the cup all round with honey, that the unsuspecting child, having first tasted the sweet, may have no fear of the bitter. So too do these act, who disguise poisonous herbs and noxious juices under the names of medicines, so that no one almost, when he reads the label, suspects the poison. (ch. 65)
The goal of church councils:
Finally, what other object have Councils ever aimed at in their decrees, than to provide that what was before believed in simplicity should in future be believed intelligently, that what was before preached coldly should in future be preached earnestly, that what was before practised negligently should thenceforward be practised with double solicitude? (ch. 59)
Classically Christian 