John Peckham

[Attributed to] John Peckham, Archbishop of Canterbury (c. 1230–1292).
De oculo morali et spirituali.
[Augsburg: Anton Sorg, not after August 1476]. (06919)

This treatise on the “Moral and Spiritual Eye” utilizes various optical phenomena to demonstrate lessons of Christian morality. One example translates: “It is proved by the science of perspective that if a viewer is deprived of direct rays or lines of sight, he cannot be sure of the size of the object he sees. Similarly, the sinner regards what he has committed by an oblique or broken line of sight, and does not recognize the degree of error in his sin.” Although this edition identifies its author as Archbishop Peckham, the treatise was probably written by Petrus de Limoges, a thirteenth-century French physician, astronomer, and cleric.