Uwe Plath and Brill are to be commended for publishing Sebastian Castellio's Contra libellum Calvini, which he wrote, in dialogue form, in 1554, as a response to John Calvin's Defensio orthodoxae fidei. Castellio's theme here, as in his De haereticis, an sint persequendi, concerned the execution of the Spanish theologian and physician, Michael Servetus, in Geneva in 1553. The burning at the stake of Servetus prompted anger from Castellio and others keen to appeal for tolerance and condemn executions for crimes of belief. Castellio's Libellum presents a dialogue between Calvin and ‘Vaticanus’ (i.e. Castellio). Plath discusses the scholarly dispute concerning the meaning of the pseudonym, Vaticanus, in his excellent twenty-three-page introduction and provides a good summary of the dispute and notes on the text itself. Castellio did not publish his Libellum in 1554. It was published by Reinier Telle in the Netherlands in 1612 in the middle of the debate between the Remonstrants and Counter-Remonstrants. Plath's critical edition provides readers not merely with a reprinting of Telle's text, but with a text as close to Catellio's original as possible (which includes the Basle Autograph-fragment). Castellio's libellum is written in an acerbic style, laced with wit and derision, as he attacks and even mocks Calvin's argument in defence of execution. Plath's edition is attractively presented and readable and contains numerous footnotes throughout. The volume is rounded off by an appendix containing Castellio's ‘Historia de morte Serveti’ and a helpful bibliography.