Giorgio Agamben writes that Christianity produced a “new ontological-practical paradigm, namely that of effectiveness, in which being and acting enter into a threshold of undecidability. If, in the words of Foucault, Plato taught the politician not what he must do but what he must be in order ultimately to act well . . . , now it is a matter of showing how one must act in order to be able to be - or, rather, of reaching a point of indifference . . . . The subordination of acting to being, which defines classical philosophy, thus loses its meaning” ( Opus Dei: An Archaeology of Duty , 63).

Agamben finds this in unexpected places - like Boethius, who on Agamben’s reading is a key example of this “transformation” of classical ontology. He quotes Boethius’s claim that “That thing has substance which furnishes from below to other accidental things a subject enabling them to be for it ‘subtends’ those things so long as it is subjected to accident,” and he explains that here “substance [is] plainly an operation that renders the accidents capable of being . . . but being, too, which they attain by means of substance, is something operative that results from this operation . . . . substance is something that is ‘taken’ and effective, and it does not have a being independent of effectuation.” Boethius’s description of substance “has no parallels in the Greek texts from which Boethius draws his terminology” (56).

Agamben knows that he is treading paths previously trodden by Heidegger, but what makes his thesis unique is the fact that he does not, like Heidegger, trace the Christian ontological difference to the doctrine of creation but to liturgical practices and sacramental theology.

He points out, for instance, that the word Boethius uses for “furnishes from below” is subministrare , derived from ministrare , which was “already part and parcel of the technical liturgical vocabulary in the age of Boethius” (56).

He is particularly taken by discussions of baptismal efficacy that grew, in part, out of the Pelagian controversy. In the distinction between opus operatum and opus operans or operantis , Agamben sees the seeds of an understanding of action, and an ontology, that ultimately comes to fruition in the modern identification of being with effect or effectiveness. By this distinction, “the ethical connection between the subject and his action is broken: what is determinative is no longer the right intention of the agent but only the function that his action carries out as the opus Dei .” Somewhat paradoxically, this separation of the agent from his action ensures at the same time that the action has its effect, no matter what, because it doesn’t depend on the actor. “This can happen, however, only at the price of dividing and emptying of its personal content the action of the priest, who, as the ‘animate instrument’ of a mystery that transcends him, exercises an action that is still in some sense his own” (25).

In liturgical and sacramental uses of the notion of effectus , further, he again sees an anticipation of later ontological developments: “While in the vocabulary of classical ontology being and substance are considered independently of the effects that they can produce, in effectiveness being is inseparable from its effects; it names being insofar as it is effective, produces certain effects, and at the same time is determined by them. Effectiveness is, that is to say, the new ontological dimension that is affirmed first in the liturgical sphere and is then to be extended progressively until in modernity is coincides with being as such” (41).

Whether or not Agamben has the details right, the twin notion that Christianity evangelized metaphysics, and that it evangelized metaphysics through liturgical theology, is, to this read, prima facie attractive, not least because it locates the novelty of Christianity not so much in the realm of ideas as in liturgical practice.