Like their predecessors throughout the late nineteenth and twentieth centuries, popes John Paul II and Benedict XVI have emphasized the importance of philosophy in the Catholic intellectual tradition. In his encyclical Fides et ratio (1998), John Paul II called on philosophers “to have the courage to recover, in the flow of an enduringly valid philosophical tradition, the range of authentic wisdom and truth.” Where the late pope spoke of an “enduringly valid tradition,” Jacques Maritain and other Thomists often have referred to the “perennial tradition” or to “perennial philosophy.” Words of Wisdom responds to John Paul's call for the development of this tradition with a much-needed dictionary of terms. As a resource for students in colleges, universities, and seminaries, as well as for teachers of the perennial tradition and interested general readers, Words of Wisdom occupies a unique place. It offers precise, yet clear and understandable accounts of well over a thousand key philosophical terms, richly cross-referenced. It also explains significant terms from other philosophical movements with which Thomism (and the Catholic intellectual tradition more generally) has engaged—either through debate or through judicious and creative incorporation. Moreover, it identifies a number of theological and doctrinal expressions to which perennial philosophy has contributed. Finally, it provides a comprehensive bibliography of works by Aquinas in English, expositions and discussions of perennial themes, and representative examples from the writings of all philosophers and theologians mentioned in dictionary entries.