Debates in mid-century French psychiatry reflected these assumptions. Were hallucinations a malfunction of the sense organs or, as Esquirol maintained, a ‘central’ phenomenon of the brain itself? Was it possible for them to co-exist with reason? Should all mystic states be regarded as hallucinations? Such questions were put to the test by Esquirol’s protégé Jacques-Joseph Moreau de Tours, who experimented with large doses of hashish in the company of a literary demi-monde that included Théophile Gautier, Gérard de Nerval and Baudelaire. He concluded that, even at the mindbending peak of its effects, hashish produced only illusions based on sensory distortion rather than ‘true hallucinations’, manufactured by the mind from whole cloth. ‘A hallucination,’ he wrote in 1845, ‘is the most frequent symptom and the fundamental fact of delirium, mental illness and madness.’ The physician and theorist of dreams Alfred Maury assumed a direct equivalence between hallucinators and the insane: ‘For what are the latter, if not minds who believe in their hallucinations as if they were serious facts?’
more from Mike Jay at the LRB here.