Jonathan sets me straight. At least partly. On my reading, Pierre Menard neither "re-wrote Don Quixote without ever having read it" nor "transcribed" it through some unknown process that rendered it an "original" composition of his own. Both ideas are belied by Borges' text. "When I was twelve or thirteen years old I read it," writes Menard in his letter to the narrator, "perhaps in its entirety. Since then I've reread several chapters attentively." Our narrator also tells us that Menard's "aim was never to produce a mechanical transcription of the original; he did not propose to copy it." Jonathan at one point suggests Menard "reproduces or 'transcribes' it through an unexplained science-fictiony device" or alternatively (and I think more plausibly) "memorize[s] sections of it and then sit down to write, but never writing down something unless he felt it as his own". Jonathan emphasises that honesty is the key to this, since in one sense what he is doing is in fact transcribing: he is "writing across" from one text to his own. It's only when he has actually appropriated the words, so that they are no longer Cervantes' but his own, that his project has succeeded. The standards by which one can evaluate this process are of course unknown.
I'm still not convinced this is exactly what Borges, Menard or the fictional literary critic had in mind. I'm entirely willing to play at being "more Borgesian than Borges" as Jonathan suggests, of course. But I need to square my understanding of the text with, especially, this description of Menard's process, provided in that same letter to the narrator:
My [Menard's] general memory of Don Quixote [from his reading], simplified by forgetfulness and indifference, is much the same as the imprecise, anterior image of a book not yet written. Once this image (which no one can deny me in good faith) has been postulated, my problems are undeniably considerably more difficult than those which Cervantes faced. My affable precursor did not refuse the collaboration of fate; he went along composing his immortal work a little a la diable, swept along by inertias of language and invention. I have contracted the mysterious duty of reconstructing literally his spontaneous work. My solitary game is governed by two polar laws. The first permits me to attempt variants of a formal and psychological nature; the second obliges me to sacrifice them to the 'original' text and irrefutably to rationalize this annihilation."
Here the suggestion is that he'll work with his memory of the story, not his memory of the the text, which he insists is as imperfect as a novelist's image of a book he's not yet written. It's out of that imaginary that he will attempt to produce a text that is identical to Cervantes'. The claim is that he succeeded in writing two chapters and part of another.
I'm being pedantic mainly for the sake of making this clear to myself. And also because something Jonathan said reminded me of another remark of Borges' in his "Note on (towards) Bernard Shaw". "The heroic aspect of the feat," says Jonathan, "[is] bridging the distance between the two sensibilities without ever cheating. The exact mechanism ... is deliberately obscure since what matters is the negotiation between the two subjectivities." In his "Note", Borges dismisses a series of literary "devices"—Lully's metaphysical discs, Mill's worry about the exhaustion of the possibilities of music, Lasswitz's "total library" (which Borges successful made his own)—because they turned the problem into "a kind of play with combinations". I think Susan Blum's "folk anthropologists" are in the same category.
Those who practice this game forget that a book is more than a verbal structure or series of verbal structures; it is the dialog it establishes with its reader and the intonation it imposes upon his voice and the changing and durable images it leaves in his memory.
I think we have to remember that Menard was not trying to do something like those patchwriters who want to know what the minimum amount of changes you have to make to a text is if you want to turn it into paraphrase. He was, as Jonathan says, attempting a "negotiation between two subjectivities" in the most difficult terrain imaginable, i.e., in the mental space that differentiates the meaning of two identical texts.