In this talk Martin Klein tries to show that the Eucharist, once again, proves to be a significant transformer of hylemorphism, namely against the background of the debate on unity and plurality of substantial forms in human being. The main object of pluralists is to account for the diachronic identity of Christ’s and accordingly every human body. It is his suspicion that substantial form pluralism by introducing a further substantial form, i.e. the form of corporeity, collapses into substance dualism. Hence, late medieval substance dualism did not evolve from the mind-body-problem, but from theological debates concerning the problem of Christ’s body being truly in the communion wafer.