 Sanches had addressed his critique of Proclus’ commentary in an earlier letter he sent to Clavius. However, while this first letter was lost, the extant letter, “Ad. C. Clavium Epistola”, demonstrates his dissatisfaction with Clavius’ Scholastic appeal to consecrated authority or Proclus. In the first letter, Sanches congratulates Clavius for his ability to demonstrate some of Euclid’s propositions, with fewer words than Proclus and even Euclid. In keeping with common opinion, he believes it is a virtue to state things as clearly as possible in order to avoid unnecessary confusion “especially in mathematics, where we should understand as much as possible through the use of our senses” (LC: 300: #10, my translation).