The doctrine of the transcendentals is a truly medieval doctrine. Up until the thirteenth century, philosophers and theologians were familiar with the study of being through the ancient philosophers and their schools, particularly Plato and Aristotle. What was important for Plato, Aristotle et al. was to offer an account of being in terms of those constitutive principles without which nothing would be. So, for example, being was taken to be accounted for in terms of participation in the forms (Plato), or through the dichotomies of substance and accident, matter and form, act and potency (Aristotle). What such projects seemed to exclude, or at least did not address explicitly, was the character of being itself. The question of the character of being itself was not explicitly elaborated until the thirteenth century, when the chancellor of the University of Paris, Philip, produced his Summa de bono (1225–8), the first eleven questions of which elaborate the doctrine of the transcendentals or what he called the communissima. Philip was quickly followed in this project by the Franciscans at the University of Paris, notably Alexander of Hales, whose Summa theologica or Summa fratris Alexandri (1245) contained a treatise on the transcendentals in Book 1.