12.

For if the knowledge of the discordant and mutually contradictory opinions of others is of any service to him who would obtain an entrance for Christian truth in overthrowing the opposition of error, it is useful only in the way of preventing the assailant of the truth from being at liberty to fix his eye solely on the work of controverting your tenets, while carefully hiding his own from view. For the knowledge of the truth is of itself sufficient both to detect and to subvert all errors, even those which may not have been heard before, if only they are brought forward. If, however, in order to secure not only the demolition of open errors, but also the rooting out of those which lurk in darkness, it is necessary for you to be acquainted with the erroneous opinions which others have advanced, let both eye and ear be wakeful, I beseech you,--look well and listen well whether any of our assailants bring forward a single argument from Anaximenes and from Anaxagoras, when, though the Stoic and Epicurean philosophies were more recent and taught largely, even their ashes are not so warm as that a single spark can be struck out from them against the Christian faith. The din which resounds in the battle-field of controversy now comes from innumerable small companies and cliques of sectaries, some of them easily discomfited, others presuming to make bold resistance,--such as the partisans of Donatus, Maximian, and Manichaeus here, or the unruly herds of Arians, Eunomians, Macedonians, and Cataphrygians and other pests which abound in the countries to which you are on your way. If you shrink from the task of acquainting yourself with the errors of all these sects, what occasion have we in defending the Christian religion to inquire after the tenets of Anaximenes, and with idle curiosity to awaken anew controversies which have slept for ages, when already the cavillings and arguments even of some of the heretics who claimed the glory of the Christian name, such as the Marcionites and the Sabellians, and many more, have been put to silence? Nevertheless, if it be necessary, as I have said, to know beforehand some of the opinions which war against the truth, and become thoroughly conversant with these, it is our duty to give a place in such study to the heretics who call themselves Christians, much rather than to Anaxagoras and Democritus.