The challenge before contemporary liturgical and sacramental theologians is to findnew means of explaining the notion of sacramental ef icacy, which would be suf icient to sustain the Christian faith and enhance worship in our contemporary society. This study argues that the complexities of the human person in today’s society have made the traditional categories and framework (like Thomas Aquinas’ theory of sanctifying grace) used to express the human person’s experience of God inadequate to enhance worship in contemporary times. It presents Bernard Lonergan’s approach as a more sustainable model that better elaborates on the position of Thomas Aquinas and The Rites of Christian Initiation of Adults (RCIA). Lonergan attempts to understand the idea of grace offered in the sacraments by beginning with human experiences. Head vocates for a liturgical and sacramental theology that enables the human person to encounter God. For him, reflection on conversion is the foundation for that new theology.