structural:expansion, structural:reformatting, structural:scholar_edition, information:extraction
Basel (1526–1528)

In 1526, he bought the rights of citizenship in Strasbourg to establish his own practice. But soon after, he was called to Basel to the sickbed of printer Johann Frobenius and reportedly cured him. During that time, the Dutch Renaissance humanist Erasmus of Rotterdam, also at the University of Basel, witnessed the medical skills of Paracelsus, and the two scholars initiated a dialogue, exchanging letters on medical and theological subjects.

In 1527, Paracelsus was a licensed physician in Basel with the privilege of lecturing at the University of Basel. At that time, Basel was a centre of Renaissance humanism, and Paracelsus here came into contact with Erasmus of Rotterdam, Wolfgang Lachner, and Johannes Oekolampad. When Erasmus fell ill while staying in Basel, he wrote to Paracelsus: "I cannot offer thee a reward equal to thy art and knowledge—I surely offer thee a grateful soul. Thou hast recalled from the shades Frobenius who is my other half: if thou restorest me also thou restorest each through the other."

Paracelsus' lectures at Basel university unusually were given in German, not Latin. He stated that he wanted his lectures to be available to everyone. He published harsh criticism of the Basel physicians and apothecaries, creating political turmoil to the point of his life being threatened. In a display of his contempt for conventional medicine, Paracelsus publicly burned editions of the works of Galen and Avicenna. On 23 June 1527, he burnt a copy of Avicenna's Canon of Medicine, an enormous tome that was a pillar of academic study, in market square. He was prone to many outbursts of abusive language, abhorred untested theory, and ridiculed anybody who placed more importance on titles than practice: 'if disease put us to the test, all our splendour, title, ring, and name will be as much help as a horse's tail'. During his time as a professor at the University of Basel, he invited barber-surgeons, alchemists, apothecaries, and others lacking academic background to serve as examples of his belief that only those who practised an art knew it: "The patients are your textbook, the sickbed is your study." Paracelsus was compared with Martin Luther because of his openly defiant acts against the existing authorities in medicine. But Paracelsus rejected that comparison, famously stating: "I leave it to Luther to defend what he says and I will be responsible for what I say. That which you wish to Luther, you wish also to me: You wish us both in the fire." A companion during the Basel years expressed a quite unflattering opinion on Paracelsus: "The two years I passed in his company he spent in drinking and gluttony, day and night. He could not be found sober an hour or two together, in particular after his departure from Basel." Threatened with an unwinnable lawsuit, he left Basel for Alsace in February 1528.