This article analyses the rhetorical strategies of Isaiah 6 and their relationship to the paradoxical commission to speak so that the audience should not understand. In particular, I look at strategies of concentration and diffusion, how the chapter directs attention to the prophet and his initiatory experience, and directs attention away from the vision of God, the moment of encounter, and the consciousness of the people. I divide the chapter into three parts (w. 1-4, 5-8, 9-13), respectively characterized by divergence, convergence, and divergence again. In the third part, the rhetorical technique is more complicated, in that the centrifugal dynamic is reinforced by failed attempts at focus. Throughout, synecdoche is the preeminent instrument both for directing attention to the participants and away from them. In the last verse, there is a shift from metonymy to metaphor as the principal poetic device, and thus a transference from a narrative, historical paradigm to a diffused alterity. The chapter is thereby decentred; since it is generally regarded as a key chapter in the book of Isaiah, the book itself is unstable. I conclude by discussing the commission as a model for the reading process, and wondering whether the metaphorical equivalence of fullness and emptiness subverts the entire rhetorical structure I have delineated.