Michael Servetus, the Spanish theologian and physician, was born in Spanish Navarre and was burned at the stake in Geneva. In the history of medicine he is remembered for having been the first to publish a description of the pulmonary circulation of the blood, and in the history of theology, he is noted for his systematic refutation of the Nicene doctrine of the Trinity. In philosophy, he developed a Christocentric pantheism that included elements from the Neoplatonic, Franciscan, and kabbalistic traditions. It should be pointed out, however, that he believed that natural philosophy should be grounded in empirical investigation.

After studying the three biblical languages as well as mathematics, philosophy, theology, and law at the universities of Zaragoza and Toulouse, Servetus, in the capacity of secretary, accompanied Juan de Quintana, the Franciscan confessor of Emperor Charles V, to the latter's coronation in Bologna. Breaking...