Should the Summa be Considered a Miracle. ─ If you ask How did it happen that this man, living six hundred years ago wrote a theology suited to the needs of all times? I answer in the words of Pope John XXII: "Doctrina ejus non potroit esse sine miraculo (His learning cannot be explained without admitting a miracle)." ~D.J. Kennedy, O.P.
Vision of St. Thomas Aquinas, by Santi di Tito. Oil on panel, 1593; San Marco, Florence.
The two online works listed below contain easy-to-read, chapter-by-chapter discussions of the Summa Theologica. Just bookmark these sites for online reference. 1.A Companion to the Summa by Walter Farrell O.P. another link: A Companion to the Summa 2.A Tour of the Summa by Paul J. Glenn
Also, these works can be found in print versions: A Companion to the Summa, generally found used and in 4 volumes, and A Tour of the Summa, in a single volume, both new and used.
A Shorter Summa: The Essential Philosophical Passages of Saint Thomas Aquinas' Summa Theologica, by Peter Kreeft. A shortened version of Kreeft's much larger Summa of the Summa, which in turn was a shortened version of the Summa Theologica. This little book (162 pages) is designed for beginners, either for classroom use or individually. A Shorter Summa contains an extensive lexicon of important terms and helpful footnotes as well on every page.