In this treatise, written in reaction to both the execution of Michael Servetus by John Calvin and the Catholic Inquisition, Castellio vehemently criticizes the concept of heresy and opposes the idea that political power should punish heretics.

Although his treatise, like Advice to a desolate France, did not succeed in preventing the French Wars of Religion, it stands as one of the earliest texts advocating for religious tolerance in history.

[1][2] This opposition reached its peak with the execution of Michael Servetus, a Protestant theologian deemed heterodox, who was burned alive in Geneva.

[1][2][3] Besides this Swiss context, he seems to have been inspired by issues related to the Anabaptists in Germany, the situation surrounding David Joris,[5] and writings by authors like Sebastian Franck.

[6] The pamphlet had a significant impact in Geneva, prompting Theodore Beza to respond the following year with his own treatise defending the execution of Servetus.