The aporia that is Beckett's mark of uncertainty, invalidation, and even hopelessness is for Joyce a rupture in certainty that makes possible ethical thought. Aporia signifies the breakdown of immediate or accessible meaning, as Beckett indicates, because the word etymologically signifies a pathless path or an impassable passage, suggesting difficulty and perplexity. In rhetoric it is an indication of real or pretended doubt. For Joyce, educated in a Jesuit tradition in which doubt and the intellectual impasse are the very bases for Catholic faith and drawn to the Celtic philosophers of uncertainty, the figures of doubt and impossibility, the undermining of determinate meaning, the path that gives way, all of these are intellectual opportunities for creativity, for path breaking, for the entertaining of possibility from within the impossible. Jacques Derrida notes that aporia as nonpassage is a form of arrest: “nonpassage because its elementary milieu does not allow for something that could be called passage, step, walk, gait, displacement, or replacement, a kinesis in general.”