ABSTRACT Although James Joyce is famous for his stylistic difficulty, perhaps no feature of his writing is more paradoxical than what may be its most conventional technique: his frequent descriptions of light, or what I term photomimesis. This essay uncovers the theoretical tensions of this outwardly simple descriptive trope. Through readings of passages from across Joyce’s oeuvre, I show how light, a classic emblem of literary beauty, repeatedly converges with literary effects that problematise the aesthetic distinctions his texts seek to establish. In Ulysses, the stubborn persistence of photomimesis undermines Joyce’s experiments with what Brian Richardson calls ‘anti-aesthetic’ prose, and thus reveals his basic commitment to good style. Yet if the photomimetic sentence remains a hidden paradigm of literary beauty, it also disrupts the coherence of Joyce’s aesthetic system. For Stephen Dedalus, light epitomises beauty in art. But the actual experiences of light narrated in Joyce’s works imply that it also produces a sensuous pleasure rigourously excluded from Stephen’s aesthetics. For Joyce, the very paradigm of literature’s aesthetic autonomy is thus also a form of non-art: photomimesis at once short-circuits Joyce’s experiment with the anti-aesthetic and violates his aesthetic ideal of radiance, or claritas, itself.