The first great summist was Peter Lombard (died 1160), author of the Books of Sentences and surnamed "Master of Sentences". The order of topics in the Books of Sentences is as follows: In the first place, the topics are divided into res and signa, or things and signs. "Things" are subdivided into: the object of our happiness, God — to this topic Peter devotes the first book; means of attaining this object, viz., creatures — the topic treated in the second book; virtues, men and angels, that is, special means of happiness and subjects of happiness — the topic of the third book; the fourth book is devoted to signs: the sacraments. How far Peter Lombard was influenced by earlier summists, such as Robert Pullen, Hugh of St. Victor and the author of the "Summa Sententiarum" which was immediately inspired by Abelard's work, historians have not determined. It is generally admitted that the Lombard was not entirely original. He deserves his renown as the first great summist chiefly because, in spite of the opposition which his work met during his lifetime, its influence grew greater in time, until in the thirteenth century it was universally adopted as a text. Notwithstanding all that hostile critics of Scholasticism have said about the dryness and unattractiveness of the medieval "Summæ", these works have many merits from the point of view of pedagogy, and a philosophical school which supplements, as Scholasticism did, the compendious treatment of the "Summæ", with the looser form of treatment of the "Quæstiones Disputatæ" and the "Opuscula", unites in its method of writing the advantages which modern philosophy derives from the combination of textbook and doctor's dissertation. The Summa Theologiae of St. Thomas Aquinas is often considered the most perfect specimen of this kind of literature. The term "Summulæ" was used, for the most part, to designate the logical compendiums which came to be adopted as texts in the schools during the thirteenth century. The best known of these is the "Summulæ Logicales" of Peter Hispanus, afterwards Pope John XXI.
The "Summa" of St. Thomas (1265-75) is still the masterpiece of theology. The monumental work of Albertus Magnus is unfinished. The "Summa de bono" of Ulrich of Strasburg (d. 1277), a disciple of Albert is still unedited, but is of interest to the historian of the thought of the thirteenth century. The theological summa of St. Antoninus is highly esteemed by moralists and economists. The "Compendium theologicæ veritatis" of Hugh Ripelin of Strasburg (d. 1268) is the most widespread and famous manual of the Middle Ages.
The chief manual of confessors is that of Paul of Hungary composed for the Brothers of St. Nicholas of Bologna (1220-21) and edited without mention of the author in the "Bibliotheca Casinensis and with false assignment of authorship by Raymund Duellius. The "Summa de Poenitentia" of Raymond of Pennafort, composed in 1235, was a classic during the Middle Ages and was one of the works of which the manuscripts were most multiplied. The "Summa Confessorum" of John of Freiburg (d. 1314) is, according to F. von Schulte, the most perfect product of this class of literature.
The Pisan Bartolommeo of San Concordio has left us a "Summa Casuum" composed in 1338, in which the matter is arranged in alphabetical order. It was very successful in the thirteenth and fourteenth centuries. The manuals for confessors of John Nieder (d. 1438), St. Antoninus, Archbishop of Florence (d. 1459), and Girolamo Savonarola (d. 1498) were much esteemed in their time