Volume one of this two-volume set includes the decrees of the ecumenical councils from Nicaea I to Lateran V. Indispensable to both Roman Catholic and Protestant historians and theologians, as well as anyone interested in the development of Christian thought and doctrine, this volume presents the decrees in their original language and in English translation. These decrees represent the authoritative distillation of Christian tradition which itself is bound together with scripture "in a close and reciprocal relationship" so that the two "form a single sacred deposit of the word of God, entrusted to the church." The original text is a reproduction of the brilliant edition by G. Alberigo and others of the decrees Conciliorum Oecumenicorum Decreta, which provides for the first time a reliable critical text for all the ecumenical councils. The English translation faces each page of the original text and is the first rendering into English of all these decrees taken together. The translators have used inclusive language throughout to emphasize the continuity of conciliar documents.

This volume includes authenticated texts and their English renderings for the first eighteen councils as well as a preface and introduction by the original languages editor, a foreword by the English language editor, a bibliography for each decree, and various commentaries and explanatory notes.