The Ark can be understood as a singular universal. In the history of philosophy we see singular universality as a paradoxical engine sparking reflection, debate and new theories. Most significant, maybe, is Aristotle's critique of Plato's conception of form. How can forms be at the same time universal (they are predicates in which individuals participate) and singular (there is 'one' of each, each one really exists)? So Aristotle posits that substance, not form, is primary (the individual being to which predicates are attached, undergoing transformation). But it is no easier to give a clear, consistent account of how substance could play this role.
It is this inability to convincingly posit either the singular or the universal as fundamental that finds a paradoxical fulfillment in Jesus Christ. As explicated by Von Balthazar, Christ is the singular universal itself: a fully adequate representation of God expressed in an individual, incarnate being (God as form, Christ as substance).
There is a certain danger in poststructuralist attempts to 'abstract' this notion of Christ into a more general 'enigmatic' signifier that signifies only itself - namely the danger of re-universalizing its singularity. There can be as many enigmatic signifiers as we want. But if there are more than one, we return to the logic we were seeking to escape.
The enigmatic signifier needs to have a proper name (a rigid designator). Nevertheless it doesn't seem possible to identify it with Jesus Christ. Why Christ only? Why not the enlightenment? Why not the philosopher's stone of hermeticism? Or the birth of language itself?
We simply it the name "Ark". "Ark" names something that has truly already happened which authorizes hope for the perfect fulfillment of human desire and commands asceticism, suffering and transfiguration