Innocent was also a notable patron of learning; he encouraged Alexander of Hales to write his Summa universae theologiae, did much for the universities, notably the Sorbonne, and founded law schools at Rome and Piacenza.
His principal works are In Gratiani Decretum commentarii (4 vols., Venice, 1578); Expositio brevis et utilis super toto psalterio (Mainz, 1474); Quaestiones spirituales super evangelic totius anni (Brixen, 7498); Summa ecclesiastica (Salamanca, 1550).
Beside the theological and political works above quoted, Occam wrote Summa Logices (Paris, 1488, Oxford, 1675) commentaries on Porphyry's Isagoge, on the Categoriae, De Interpretatione and Elenchi of Aristotle.
His De arte seu de articulis catholicae fidei is a Summa of Christian theology, but with a greater infusion than usual of philosophical reasoning.
The name Geber has long been used to designate the author of a number of Latin treatises on alchemy, entitled Summa perfectionis magisterii, De investigatione perfectionis, De inventione veritatis, Liber fornacum, Testamentum Geberi Regis Indiae and Alchemia Geberi, and these writings were generally regarded as translations from the Arabic originals of Abu Abdallah Jaber ben Hayyam (Haiyan) ben Abdallah al-Kufi, who is supposed to have lived in the 8th or 9th century of the Christian era.
This was Lucas Paciolus (Lucas de Burgo), a Minorite friar, who, having previously written works on algebra, arithmetic and geometry, published, in 1494, his principal work, entitled Summa de Arithmetica, Geometria, Proportioni et Proportionalita.
In his Summa he declares that as there are seven chief sins, either original or of act, so there must be seven sacraments to remedy them; but he only enumerates six, namely baptism and the sacraments of confirmation, of the altar, of penance, last unction and matrimony.
One of these, Summa de assumpto homine, is of a theological character, dealing with the humanity of Christ; the other, Summa de matrimonio, is a legal argument, to the effect that the essential fact in marriage is neither, as Gratian maintains, the copula, nor, as Peter Lombard, consent by verba de praesenti, but mutual traditio.
Nevertheless Hugo, by the composition of his Summa sententiarum, endeavoured to give a methodical or rational presentation of the content of faith, and was thus the first of the so-called Summists.
His Summa universae theologiae secundum Unitarios (1787), Socinian with Arminian modifications, was accepted by Joseph II.