The doctrine of transubstantiation was presented formally in Canon 1 of the Fourth Lateran Council of 1215, which was presided over by Innocent III. Transubstantiation, as explained explicitly in the canon, involved the replacement or transformation of one substance (the bread or the wine) by another (the body or the blood of Christ). This formal record of ‘orthodox’ eucharistic doctrine was the implicit target of much of Wyclif’s criticism of contemporary conceptions of material change in the host. It entailed necessarily for him that the substances of the bread and the wine had to have been annihilated, and that their accidents had therefore to exist without subjects. Many theologians had published versions of this theory, including Thomas Aquinas, but Wyclif’s metaphysical system could admit neither the possibility of annihilation nor the possibility of accidents existing without substantive subjects. He outlined his position in a late philosophical treatise, On the Externally Productive Power of God (1371/2), but its controversial potential ostensibly went unnoticed.