§1. Pure Literature is shorthand for what literature ought to be: work where the writing itself matters as much as what it is about. The term borrows from mathematics, where “pure” means study for its own sake, pure anarchic expression of the human consciousness.
The core idea is simple: literary merit can be defined, among other things, on the difficulty of translating the work into another medium. If you can retell the story equally well as e.g. a film, why pick literature? (definitely not in music, though, that’s impossible, music’s the purest of art forms!). We’re not the 19th century where Literature had practically no competition over the minds. Now it has to do something that nothing else can, something unique on the form level to resolve dramatic tension rather than rely solely on clean prose and plot.
§2. Pure Literature descends from a tradition that treats language as material, as sound, even as a musical instrument. Prose can, and must, at least strive for or be inspired by technical virtuosity to drive literary innovation and discoveries.
§3. Pure Literature defamiliarises perception of the world, creates a parallel world that can be surreal, absurd, and yet remain eerily reminiscent of reality.
Defamiliarisation is a technique of making the familiar strange so you actually see the real innermost essence of things, beings, phenomena. Realism can only mirror the surface, but it often falls short in revealing the structural abstractions underneath: the world of expressions, subtle feelings, perception, subconscious, images, that describe the real better than the real itself can.