Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Donatist Controversy.: Chapter 96

Chapter 96.—218.  Petilianus said:  "But what reason is there, or what inconsistency of emptiness, in desiring communion with us so eagerly, when all the time you call us by the false title of heretics?"

219.  Augustin answered:  If we so eagerly desired communion with heretics, we should not be anxious that you should be converted from the error of heresy; but when the very object of our negotiations with you is that you should cease to be heretics, how are we eagerly desiring communion with heretics?  For, in fact, it is dissension and division that make you heretics; but peace and unity make men Catholics.  When, then, you come over from your heresy to us, you cease to be what we hate, and begin to be what we love.