 Wyclif's logico-metaphysical works were very influential at Oxford at the end of the 14th century and the beginning of the 15th. Among the authors who followed his doctrines (the so called Oxford Realists), William Penbygull (+1420) was almost certainly the most faithful to the master, since his extant writings appear to be essentially devoted to a defence and/or explanation of Wyclif's main philosophical theses. Notwithstanding such an attitude, Penbygull made an original contribution to logic by developing a new theory of identity, which solved the problems that Wyclif's analysis of predication had raised, and by refining Wyclif's theory of predication itself. 