Jerónimo Muñoz’s Reception of Proclus’ In Euclidem: Philosophy of Mathematics and an Attempt to Prove the Parallel Postulate

The goal of this paper is to show – by way of a case study – how the contents of Proclus’ Commentary on the First Book of Euclid’s Elements were incorporated into university teaching in the sixteenth century. I analyse the impact of Proclus on the works of the Spanish mathematician and university professor Jerónimo Muñoz (ca. 1520–1591). In order to do so, I examine two manuscripts: Adnotationes in commentaria Procli super Euclidem (MS Vat. Lat. 6996), and Astrologicarum et geographicarum institutionum libri sex (MS Vat. Lat. 6998). I show that the contents of Proclus’ commentary pervade Muñoz’s mathematical writings and influence his mathematical ontology, his classification of mathematical disciplines, and the history and terminology of geometry that he adopts. Moreover, I expound on how Proclus’ text inspired Muñoz to maintain that the fifth postulate was a theorem, leading him to attempt a demonstration of it which pre-dates knowledge in the Latin West of Naṣīr ad-Dīn’s (1201–1274) previous attempt.