The reader is offered the 2nd (corrected) edition of the complete translation of the treatise “On the Trinity” by the outstanding Christian thinker St. Aurelius Augustine (Blessed) (354–430 AD). This work, in its significance, stands on a par with such of his works as “Confession” and “On the City of God”, and is devoted to a systematic presentation of the doctrine in which Augustine saw the basis of Christian doctrine. Beginning with the exegesis of the texts of Holy Scripture, Augustine defends the dogma of the Trinity from a philosophical position, using analogies with the natural world and especially with the forms of activity of the human mind. The text of the treatise is preceded by Augustine's 174th letter as a preface and concludes with an excerpt from his later work "Revisions" (Retractationes). Addressed to philosophers, theologians and all readers interested in the heritage of world classical thought. 2nd edition, revised.