In this classic book, John of Damascus laboured to form one complete, clear, and brief theological work that would summarize all Christian doctrine that had been passed down and agreed upon. The following was said of the book: The result was an inexhaustible storehouse of tradition in which nothing is to be found that has not been either approved by the ecumenical synods or by the established leaders of the Church. 

He followed, mostly Gregory of Nazianzus, who, from the great accuracy of his education in divine matters, earned the title "The Theologian", and who has left scarcely any chapter of Christian learning untouched, and is free from any taint of the slightest error. John had read his books so carefully that he seemed to hold them all in the embrace of his memory. So that throughout this work you may hear not John of Damascus so much as Gregory the Theologian expounding the mysteries of the true orthodox faith. John further made use of Basil the Great, Gregory of Nyssa, Nemesius, bishop of Emesa in Syria, Cyril of Alexandria, Leo the Great, Leontius of Byzantium, the martyr Maximus: also Athanasius, Chrysostom, Epiphanius, and, not to mention many others. From all these he culled on every hand the flower of their opinions, and put together the most sweet honey of soundest doctrine. For his goal was, not to form views of his own or anything novel, but only to collect into one single theological work the opinions of the ancients.