[1] It rejected the Christian doctrine of the Trinity and the concept of predestination, which had both been considered fundamental since the time of St. Augustine and emphasized by John Calvin in his magnum opus, Institutio Christianae Religionis.
It also contained, incidentally and by way of illustration, groundbreaking views on pulmonary circulation, a discovery Servetus made independent of the Arab Muslim physician Ibn Al Nafis, and one which challenged the incorrect teachings of Galen.
[2] After Jean Frellon, a Lyon bookseller, sent a copy of Christianismi Restitutio to the theologian John Calvin,[3] Servetus was arrested by the Inquisition in Vienne, but he managed to escape from prison.
With the continued help of John Calvin—whose doctrines had been criticized in letters published in the book[4] and who thought him a delirious braggart[α]—Servetus was later captured in Geneva and found guilty of spreading heresies.
[6][7][8] Servetus' discussion of the pulmonary circulation in Christianismi Restitutio in the middle of the 16th century is often recognized as the most accurate and complete description at that time.