Feuerbach died in Frankfurt on May 29, 1833 — just months before Hauser’s own death. His cause of death was described as a stroke, but his family believed he had been poisoned. Some accounts suggest he had been pursuing information about Hauser’s origins more aggressively in the final months of his life and had come to believe he was close to a significant discovery. Whether there is any documentary support for the poisoning claim is not established in sources accessible for this article. What is certain is that his death came in the same year as Hauser’s, that both deaths remained subjects of speculation, and that the coincidence was noted by contemporaries and later investigators alike.
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## The Prince Theory: What It Claimed
The theory that Kaspar Hauser was the hereditary prince of Baden developed gradually after his appearance and reached a coherent form over the following decades. Its essential elements are as follows.
On September 29, 1812, a son was born to Grand Duke Charles of Baden and his wife, Stéphanie de Beauharnais, the adopted daughter of Napoleon Bonaparte. This child was the heir to the Grand Duchy. He reportedly died on October 16, 1812, at seventeen days old.
The theory holds that the child did not die. Instead, it claims, he was secretly exchanged for a dying infant by or at the direction of the Countess of Hochberg — the morganatic wife of the previous Grand Duke, whose own sons stood to inherit the Baden succession if Charles and Stéphanie produced no surviving heir. By removing the legitimate heir and substituting a dying infant, the theory proposes, the Countess of Hochberg cleared the succession path for her own sons.