As he taught and wrote his famous theological treatises, he drew upon Aristotle and reoriented Plato and Augustine so as to build a philosophical foundation of metaphysics and epistemology that remains fundamentally important today.
One can indeed say that in his articulation of the metaphysics of Esse and in his integrated epistemological realism that does justice to the interplay of sensation and spiritual intelligence, St. Thomas has laid down the foundations for authentic philosophical as well as theological development. Although Catholic theology is far from monolithic, the best and most coherent contemporary efforts to understand the human being, the world, and the mystery of God have as their touchstone the metaphysics and epistemology of St. Thomas. He insures that thinking, no matter how adventuresome it may be in its unfolding, does not lose its bearings.
For a time after the Second Vatican Council, it seemed as though this great Catholic Doctor was destined to be forgotten, drowned in a sea of secular humanist ideologies, moral relativism, and psychoanalysis. But St. Thomas is making a strong return. His greatest twentieth century follower recognized in Thomas's principles a fountain of creative insight that made it possible to engage contemporary issues. Jacques Maritain predicted, in the midst of the post-Conciliar turmoil of 1968, that Thomas's foundational contribution would endure:
"St. Thomas..., humbly and without putting in a claim, brought metaphysical wisdom to the most basic and universal degree of intuitive grasp possible to reason. A metaphysics of 'esse,' a metaphysics born from the intuition of the act of existing--and whose primary object is this primordial and all-embracing intelligible reality--has the capacity to welcome, recognize, honor, set to rights all that is" (from The Peasant of the Garonne, 1968).