Editor’s Preface ———————————— This fourth volume of St. Augustin’s Works contains his polemical writings in vindication of the Catholic Church against the heresy of the Manichæans, and the schism of the Donatists.  The former are contained in Tom. II. and VIII., the latter in Tom. IX., of the Benedictine edition. Like the preceding volumes, this also is more than a reprint of older translations, and contains important additions not previously published. I.— Seven Writings Against the Manichæan Heresy .  Four of these were translated by the Rev. Richard Stothert , of Bombay, for Dr. Dods’ edition, published by T. & T. Clark, Edinburgh, 1872, and revised by Dr. Albert H. Newman , of Toronto, for the American edition.  The other three treatises are translated, I believe for the first time, by Dr. Newman for this edition.  (See Contents.) The Edinburgh translation, especially of the first two treatises, is sufficiently faithful and idiomatic, and needed very little alteration by the American editor, who compared it sentence by sentence with the Latin original, and made changes only where they seemed necessary. This part of the volume is also enriched by an introductory essay of Dr. Newman , which embodies the literature and the results of the most recent as well as the earlier researches concerning that anti-Christian heresy. II.— The Writings Against the Donatists .  These were well translated by the Rev. J. R. King, of Oxford, and are slightly revised by Dr. Hartranft , of Hartford, after a careful comparison with the Latin. The literary introduction of Dr. Hartranft, in connection with the translator’s historical preface, will place the reader in the situation of the controversy between the Catholic Church and the Donatists at the time of St. Augustin. In both sections the treatises are arranged in chronological order. The fifth volume will contain the writings of St. Augustin against the Pelagians and Semi-Pelagians.  It is in the hands of the printer and will be published in October. Philip Schaff . New York , June, 1887.