Sacramental theology has been grappling with the trinitarian mystery in recent years, trying to appropriate the pneumatic dimension of Christian liturgy which was all but lost in the West. Attempts to find the Spirit through exclusive recourse to symbolic and linguistic models of sacrament, however, have backfired because the Spirit's mission in the trinitarian economy requires a 'hidden visage.' In this work, an alternate model, 'efficacious engagement,' is developed to explore the way that human identity is formed by participation in ritual and how grace can be experienced as an embodied reality. Applying this phenomenological and theoretical model to the postconciliar Roman rite of infant baptism reveals a complicated ritual dynamic that mirrors the dynamism of the Godhead. The study then explores how infants participate bodily in the trinitarian relations and even allow the Christian assembly to renew itself as Body of Christ. Infant baptism thus becomes an economic reality, one that reveals significant aspects of the trinitarian manifestation in salvation history. Finally, the observations on trinitarian and sacramental economies at work in infant baptism are explored in terms of sign, symbol, and the problem of the gift.