  It has been argued (by Pouillion and others) that Philip’s discussion of the transcendentals in Summa de bono represents the earliest formal treatise on the transcendentals in the history of Western philosophy (see Pouillion 1939, Aertsen 2012). About ten years earlier, William of Auxerre also discussed the relationship between being and goodness; he raises the issue of whether being and being good are the same. But in resolving this issue, William never considers the central issue of the transcendentals, the idea that they are extensionally equivalent while intensionally different. It appears that Philip is the first to do so.  MacDonald argues that Philip’s greater familiarity with the metaphysical works of Aristotle and the Arabic commentators accounts for the startling innovations of his work on the transcendentals (MacDonald 1992). It is likely that Philip encountered the fundamental notion of extensional equivalence and intensional difference in the work of the Arabic commentators of Aristotle; both Avicenna and Averroes argue that unity and being have the same extension while differing conceptually. Philip extends this idea to include not only being and unity, but also the true and the good. Philip’s work in turn sets the stage for the development of this topic throughout the thirteenth century, influencing the work of such notable thinkers as Alexander of Hales, Albert the Great, and Thomas Aquinas (see Aertsen 2012).