Theosis and the Morality of Happiness: Investigating the Implications of the Deification Doctrine in Aquinas

This thesis examines the implications of a connection between the doctrine of deification or theosis (often summarized by the patristic axiom that God became man so that man might become God) and a Christian morality of happiness, an understanding of the moral life as that which comprises our true human flourishing—a transformative growth in virtue by which we grow in our capacity to realize our final telos of union with God. Deification, traditionally more strongly associated with Eastern Christian theology, has not typically been discussed in relation to the morality of happiness, arising primarily within the discourse of the contemporary West’s moral theology. Yet, recent scholarship has argued for deification’s presence within the Western tradition, particularly in the work of Thomas Aquinas, whose moral framework is widely regarded as a paradigmatic expression of a morality of happiness. In light of these developments, this study investigates whether contemporary interpretations of deification in Aquinas can contribute meaningfully to an understanding of Christian ethics as a morality of happiness. It does so by first clarifying the concept of a Christian morality of happiness, then examining the perceived connection between deification and moral transformation in contemporary Eastern theologians. Finally, it analyzes recent scholarly readings of deification in Aquinas for potential insights into this view of the moral life and evaluates their novelty and value to the West's ongoing discussion. The result of this investigation argues that although the concept of deification does not introduce a fundamentally new element to the Western morality of happiness beyond what is already expressed through Aquinas’s theology of grace and sanctification, highlighting deification components within his account of grace and the moral life may encourage an even stronger emphasis on the personal nature of the grace needed to live the Beatitudes, as the indwelling of the Holy Spirit, and the relational and transformative meaning of Christ’s death and resurrection. Such emphasis may help to counter reductive accounts of grace as mechanistic and salvation as merely juridical, thereby reinforcing the coherence of a morality of happiness. Furthermore, scholars’ readings of deification in Thomas may offer some contributions more broadly to the post-Vatican II project of renewal in moral theology, returning to the cohesive moral and theological framework of the Church Fathers.