He has inhibited discussion by designating admonition as the method of dealing with a heretic- and the first method, too, because he is not a Christian. This is so that he would not seem to require correction again and again and before two or three witnesses as though he were a Christian. He ought to be corrected for the very reason that he is not to be disputed with. In addition, this is said because a controversy over the Scriptures can, clearly, produce no other effect than help to upset either the stomach or the brain.
TertullianThus the connection of the Father in the Son, and of the Son in the Paraclete, produces three coherent Persons, who are yet distinct One from Another. These three are one [thing], not one [Person], as it is said, 'I and my Father are One,' in respect of unity of substance not singularity of number.
Tertullian