The Brain in a Vat and the Fourth Proposition: Why the Constitution of the Psychoanalytic Subject Exceeds Computational Sufficiency
Preprints.org June 25, 2026 Hudson Augusto Rodrigues Bonomo preprint
Starting from a Large Language Model fabricating a false reference to psychoanalyst Sándor Ferenczi, this essay traces a genealogy from Descartes's evil demon to the LLM as a technical realization of a closed-cognition fantasy. It interrogates a shared presupposition in Putnam's brain-in-a-vat thought experiment, Bostrom's simulation trilemma, and the project of artificial general intelligence: that mental operations can be preserved when the world that gave rise to them is removed. Through four converging routes—Putnam's semantic externalism, Winnicott's theory of the facilitating environment, the Ferenczian wise baby, and Lacanian topology—the author introduces a fourth proposition: the constitution of the psychoanalytic subject, divided by language and founded in lack and desire, exceeds what computational sufficiency can produce. LLM hallucination is read as a diagnostic illustration of limits of generation without verification.