Thesis advisor: Oliva Blanchette / This dissertation is a synthetic exercise in philosophy and theology, proceeding from the perennial question: "What is the specific difference between sacrament and superstition?" It answers that the difference lies in the order of revelation. Sacraments are a form of revealed praxis, and only the divine guaranty of revelation distinguishes them from other forms of human action, including superstitious action. Revelation takes shape in historical sensible signs demanding human interpretation, such as inspired scripture. These revealed signs also include precise human actions, however, in the form of the prescriptions of sacramental praxis. As the words of Scripture do not signify merely human intentions, but express the divine will, so sacramental action signifies a divine intention, not a purely human intention, in the form of this precise praxis. Sacraments, therefore, far from attempting some kind of natural purchase on the supernatural, in fact demand the opposite: the surrender of the human to the divine will, the admission of human insufficiency. This answer is based on a theological appropriation of Maurice Blondel's philosophical investigation of human action in his early philosophical work Action (1893), in which he rehabilitates the question of the supernatural on a properly philosophical footing by establishing a hypothetical necessity for a supernatural complement to human action. Blondel and Aquinas, therefore, both find the point of heterogenous insertion for the supernatural in human subjectivity: in the virtues for Aquinas, in voluntary human action for Blondel. The dialectic of Action (1893) hinges on the phenomenon of superstitious action, which functions as a middle term in the dialectic. Superstition for Blondel corresponds to an attempt at human `self-sufficiency': actively placing in a finite object of the will the transcendent perfection that can only be received passively as gift from outside the natural order, by insertion of a heterogenous factor in the human action. Given that human action is irreducible in Blondel's philosophy and even thought itself is a form of action, so superstition works its way into all forms of human practice, including intellectual pursuits like philosophy and theology, giving rise to `closed' and self-sufficient philosophical and theological systems. Moreover, Blondel audaciously turns Kant's accusation of superstition against sacraments around, arguing that it is the extreme rationalists, not the unlearned devout, who are guilty of the most insidious form of superstition by effectively fetishizing their own thought, finding there the completion that Blondel's dialectic demonstrates to be impossible in the natural order. Sacramental action, by contrast, since it requires submission of human to divine will and the admission of human insufficiency, it is at the very antipodes of superstition. The theological appropriation of Blondel's philosophy provides a heuristic in sacramental theology, since it entails that the supernatural efficacy of the sacraments cannot be attributed, even partially, to the natural efficacy of human action. It is hard to see how post-conciliar theories of `symbolic efficacy' avoid superstition, therefore, since they attempt to find in natural human action the heterogenous supernatural that cannot be reduced to the merely naturally perceptible. / Thesis (STD) — Boston College, 2015. / Submitted to: Boston College. School of Theology and Ministry. / Discipline: Sacred Theology.