This study aims to present a comparative analysis of philosophical theories of universals espoused by the foremost representatives of the three main schools of early modern scholastic thought. The book introduces the doctrines of Francisco Suárez, S.J. (1548–1617), the Thomist John of St. Thomas, O.P. (1589–1644), and the Scotists Bartolomeo Mastri da Meldola, O.F.M. Conv. (1602–1673) and Bonaventura Belluto, O.F.M. Conv. (1600–1676). The author examines in detail their mutual doctrinal delineation as well as the conceptualist tenet of the Jesuit Pedro Hurtado de Mendoza (1578–1641), whose thought constitutes an important systematic point of comparison especially with Suárez’s doctrine. The book offers the first comparative elaboration of the issue of universals, in both its metaphysical and its epistemological aspects, in the era of second scholasticism.