Abstract
This thesis defends the Catholic doctrine of the Filioque—the belief that the Holy Spirit proceeds from both the Father and the Son—by engaging with contemporary objections from Eastern Orthodox theology. Centering on the thought of St. Thomas Aquinas, it aims to demonstrate that Aquinas’s Trinitarian theology, particularly his understanding of divine personhood as subsistent relation, aligns with Orthodox emphases on relationality. In doing so, the study seeks to open ground for ecumenical dialogue and greater understanding between Catholics and Orthodox Christians.
The first chapter surveys contemporary Orthodox Trinitarian theology and common objections to the Filioque. Drawing on Aquinas’s metaphysical framework, the thesis introduces his understanding of the Trinity, especially his view that the divine persons are subsistent relations. This backdrop clarifies Aquinas’s arguments in favor of the Filioque as well as his potential responses to common Orthodox objections.
Finally, the thesis contends that contemporary Orthodox theologies of personhood—especially the emphasis of relationality—can be addressed maintained the Thomistic framework. By doing so, it suggests that both traditions may find more common theological ground than previously acknowledged, contributing to more fruitful ecumenical engagement.