Sebastian Castellio and the question of tolerance

Read the PDF edition (2 pages)

The Reformed world was not a world of tolerance. Calvin's Geneva executed the Spanish physician and theologian Michael Servetus for heresy in October 1553. The execution provoked a debate on the right of Christian authorities to kill heretics. The most important voice in this debate came from Basel. Sebastian Castellio, a French humanist who had been rector of the college of Geneva and had left the city after a conflict with Calvin, lived in Basel as a corrector for Oporinus and later as professor of Greek at the university. In 1554, he published under a pseudonym a collection of texts against the persecution of heretics, De haereticis an sint persequendi, Whether heretics should be persecuted. He also wrote a reply to Calvin's defence of the execution of Servetus, which was printed only in 1612.¹

In this reply, Castellio wrote a sentence that has become one of the classic statements of the principle of tolerance: to kill a man is not to defend a doctrine; it is to kill a man. He argued that no human authority could claim certainty in matters of faith that would justify taking a life, that faith could not be compelled, and that the persecution of dissenters contradicted the spirit of Christ. Castellio's arguments had little immediate effect, but they became an important source for the later development of the idea of religious freedom.

Castellio's presence in Basel is significant. The city, although Reformed and subject to moral discipline, tolerated the presence of dissenters who could not live in Geneva or elsewhere, as long as they did not cause public scandal. Castellio, the Italian refugees Celio Secondo Curione and Bernardino Ochino, and others who held unorthodox views found in Basel a refuge and a press. This relative tolerance, which was limited and sometimes precarious, made Basel a place of intellectual freedom in the Reformed world. It belongs to the history of the openness that a financial centre needs.

A financial centre that wants to attract clients from different countries, cultures and religions must offer them security, predictability and respect for their private affairs. It cannot demand that they share its religion or its politics. The toleration of diversity, which Basel practised imperfectly in the sixteenth century, became a condition of its commercial and financial success in the following centuries. It also raised the question, which remains central today, of the limits of this tolerance: whether a financial centre should accept the money of clients whose activities it disapproves of, and where the line between respect for privacy and complicity in wrongdoing lies. The modern rules on money laundering, sanctions and politically exposed persons, examined in Part E, draw this line in legal terms.

Notes

1. On Sebastian Castellio (1515–1563), his activity in Basel, De haereticis an sint persequendi (1554, under the pseudonym Martinus Bellius) and Contra libellum Calvini (written 1554, printed 1612), see HLS, article "Castellio, Sebastian". To be verified. ↩

For general information only. This article does not constitute legal or tax advice, does not replace advice on an individual case and creates no lawyer-client relationship. It reflects the legal position as of August 2025.