 In the sixteenth century, Pythagorean influence was particularly important in the development of astronomy. The Polish astronomer Copernicus (1473–1543), in the Preface and Dedication to Pope Paul III attached to his epoch making work, On the Revolution of the Heavenly Spheres, reports that, in his dissatisfaction with the commonly accepted geocentric astronomical system of Ptolemy (2nd century CE), he laboriously reread the works of all the philosophers to see if any had ever proposed a different system. This labor led him to find inspiration not from Pythagoras himself but rather from later Pythagoreans and in particular from Philolaus. Copernicus found in Cicero (Ac. II 39. 123) that the Pythagorean Hicetas (4th century BCE — Copernicus mistakenly calls him Nicetas) had proposed that the earth revolved around its axis at the center of the universe and in pseudo-Plutarch (Diels 1958, 378) that another Pythagorean, Ecphantus, and Heraclides of Pontus (both 4th century BCE), whom Copernicus regarded as a Pythagorean, had proposed a similar view. More importantly, he also found in pseudo-Plutarch that the Pythagorean, Philolaus of Croton (5th century BCE), “held that the earth moved in a circle … and was one of the planets” (On the Revolutions of the Heavenly Spheres 1. 5, tr. Wallis).