Nabokov's fiction is informed by a two-world vision: implicit throughout his writing is a distinction between the world of the senses and another, supersensory realm intuited to lie beyond. Not­withstanding his avowed antipathy to Plato, the metaphysic reflected in his work is in all essential respects Platonic or Neoplatonic, an unhappy dualism constantly striving towards an ideal monism. In different ways -- through art, chess, love, madness, suicide -- all his major characters are trying to leave the Platonic cave and make their way into the sunshine, into those "other states of being where art .•. is the norm." His novels may be read as the story of these attempts. The thesis is divided into three main sections. Part One ("Thematism") attempts a broad conspectus of Nabokov's metaphysical and epistemological attitudes, concentrating on the themes of time and death in his fiction. Part Two ("Figuration") then focusses on a number of characteristic Nabokovian motifs or image-complexes under the three headings of transparency, reflectivity and circu­larity/spirality. In each of these figures, or pairs of figures, one member is typically associated with the world of phenomenal reality (opaque, reflected, circular), the other with an intuited noumenal realm (transparent, specular, helical). Part Three ("Inter­textuality") concludes with intertextual readings in two novels: Invitation to a Beheading is seen to develop its idealist metaphysic through an elaborate gnostic-Neoplatonic subtext, while Ch. 14 of Bend Sinister is read as in part a meditation on, and reaction against, the materialistic monism of ancient and modern atomism. Nabokov's metaphysical code, it is concluded, belongs broadly within the tradition of the philosophia perennis, though his ambi­valent attitude towards the self, and the idea of loss of self, guards against any naively optimistic mysticism. Nonetheless, and despite his reputation for formal radicalism and technical inno­vation, the values embodied in Nabokov's work remain deeply tradi­tionalist.