Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Manichæan Controversy.: Chapter 11

Chapter 11.—Manichæus Promises Truth, But Does Not Make Good His Word.

12.  "These," he says, "are wholesome words from the perennial and living fountain; and whoever shall have heard them, and shall have first believed them, and then shall have observed the truths they set forth, shall never suffer death, but shall enjoy eternal life in glory.  For he is to be judged truly blessed who has been instructed in this divine knowledge, by which he is made free and shall abide in everlasting life."  And this, as you see, is a promise of truth, but not the bestowal of it.  And you yourselves can easily see that any errors whatever might be dressed up in this fashion, so as under cover of a showy exterior to steal in unawares into the minds of the ignorant.  Were he to say, These are pestiferous words from a poisonous fountain; and whoever shall have heard them, and shall have first believed them, and then have observed what they set forth, shall never be restored to life, but shall suffer a woful death as a criminal:  for assuredly he is to be pronounced miserable who falls into this infernal error, in which he will sink so as to abide in everlasting torments;—were he to say this, he would say the truth; but instead of gaining any readers for his book, he would excite the greatest aversion in the minds of all into whose hands the book might come.  Let us then pass on to what follows; nor let us be deceived by words which may be used alike by good and bad, by learned and unlearned.  What, then, comes next?

13.  "May the peace," he says, "of the invisible God, and the knowledge of the truth, be with the holy and beloved brethren who both believe and also yield obedience to the divine precepts."  Amen, say we.  For the prayer is a most amiable and commendable one.  Only we must bear in mind that these words might be used by false teachers as well as by good ones.  So, if he said nothing more than this, all might safely read and embrace it.  Nor should I disapprove of what follows:  "May also the right hand of light protect you, and deliver you from every hostile assault, and from the snares of the world."  In fact, I have no fault to find with the beginning of this epistle, till we come to the main subject of it.  For I wish not to spend time on minor points.  Now, then, for this writer’s plain statement of what is to be expected from him.