Augustine of Hippo, Against Two Letters of the Pelagians II.4: The Two Contrary Errors

Let the Pelagians, then, cease to object to the catholics that which they are not, but let them rather hasten to amend what they themselves are; and let them not wish to be considered deserving of approval because they are opposed to the hateful error of the Manicheans, but let them acknowledge themselves to be deservedly hateful because they do not put away their own error. For two errors may be opposed to one another, although both are to be reprobated because both are alike opposed to the truth. For if the Pelagians are to be loved because they hate the Manicheans, the Manicheans should also be loved because they hate the Pelagians. But be it far from our catholic mother to choose some to love on the ground that they hate others, when by the warning and help of the Lord she ought to avoid both, and should desire to heal both.