He denied the real existence of metaphysical universals and advocated the reduction of ontology. Platonic realism is realism regarding the existence of universals or abstract objects. The problem of universals is an ancient problem in metaphysics about whether universals exist. Realists posit the existence of independent, abstract universals to account for attribute agreement. This study sparked studies into typological universals of color terminology. Metaphysical realism uses the identity of "universals" to compare and identify particulars. Platonic Forms were the first universals posited as such in philosophy. There are many philosophical positions regarding universals. Logical methods were adopted for explanation of linguistic universals by Theo Vennemann. If it were, it would not be able to understand universals, which are immaterial. There was debate between the realists and the nominalists over the concept of "universals". This approach appealed to Greenberg, who was interested in discovering linguistic universals. Anthropologists see social rituals as one of many cultural universals. Medieval realism developed out of debates over the problem of universals. Their efforts undermined the prevailing Platonic idea of universals.