Answer
The answer "incurable" refers to Friedrich Hölderlin's mental health condition when he was admitted to a clinic in Tübingen in 1806. His symptoms included delusions, hallucinations, and incoherent speech, leading doctors to deem his condition incurable by the medical knowledge of the time. Hölderlin spent the rest of his life under the care of a carpenter's family in Tübingen, where he continued to write poetry despite his illness.