ABSTRACT
The medieval controversy over universals was rooted in a crucial disagreement between Plato and Aristotle. While Plato wanted to explain the natural order and the cognizability of the material world by postulating immaterial and mind-independent ideal Forms, Aristotle argued that it was entirely mysterious how a separate Form such as Horseness, say, could account for the substantial identity of each concrete material horse. Apart from Aristotle himself, three main sources deeply influenced this medieval debate. First, the very formulation of the problem was standardly borrowed from Porphyry’s introduction to Aristotelian logic. Second, the debate over universals that continued to be lively for a while in Parisian schools. The next major intervention in the debate came from John Duns Scotus’s younger Franciscan confrere William of Ockham, who energetically revitalized the nominalist position. His main target, as can be expected, was immanent realism.
