Medina studied theology at the University of Salamanca under the celebrated professor Francisco de Vitoria. His life was devoted almost entirely to teaching theology at Salamanca, first in the chair of Durandus, afterwards as principal professor. He was appointed to the "cathedra primaria" after a successful concursus, in public, against the learned Augustinian scholar Juan de Guevara (1518-1600). He died at Salamanca in 1581.
Although he was well versed in Greek and Hebrew, devoted his life almost entirely to teaching theology, and all his writings preserved are theological, being principally commentaries on the Summa Theologica of St. Thomas.
Works
Medina's principal works are commentaries on Thomas Aquinas. He was the first prominent exponent (and possibly the first exponent) of the doctrine of probabilism, which he sets out in his commentary on the ‘Prima secundae’ of Thomas Aquinas (1572). Medina's probabilist doctrine consisted of the contention that if two opinions are probable in unequal degree, the less probable may be followed (Si est opinio probabilis, licitum est eam sequi, licet opposita probabilior sit); in moral theology, the consequence of probabilism is that if the licitness of an action is in doubt, it is lawful to choose a probable opinion favouring liberty rather than a more probable opinion favouring the law. This doctrine was soon adopted by other Dominicans, notably Domingo Báñez, and the notion of the probable was elaborated by Jesuits as well as Dominicans; eventually Jesuits became the principal proponents of the doctrine and Dominicans its principal opponents.
