A lengthened conflict, then, having been maintained concerning all heresies by us who, at all events, have not left any unrefuted, the greatest struggle now remains behind, viz., to furnish an account and refutation of those heresies that have sprung up in our own day, by which certain ignorant and presumptuous men have attempted to scatter abroad the Church, and have introduced the greatest confusion among all the faithful throughout the entire world. For it seems expedient that we, making an onslaught upon the opinion which constitutes the prime source of (contemporaneous) evils, should prove what are the originating principles of this (opinion), in order that its offshoots, becoming a matter of general notoriety, may be made the object of universal scorn.
Reproduced in full. Translation: Ante-Nicene Fathers, vol. 5 (Roberts and Donaldson, 1886), public domain (Public domain).