 Copernicus reports to the Pope that he was led by these earlier thinkers “to meditate on the mobility of the earth.” Pythagorean influence on Copernicus was not limited to the notion of a moving earth. In the same preface he explains his hesitation to publish his book in light of the pseudo-Pythagorean letter of Lysis to Hipparchus, which recounts the supposed reluctance of the Pythagoreans to divulge their views to the common run of people, who had not devoted themselves to study (for further Pythagorean influences on Copernicus see Kahn 2001, 159–161). A number of the followers of Copernicus saw him as primarily reviving the ancient Pythagorean system rather than presenting anything new (Heninger 1974, 130 and 144, n. 131); Edward Sherburne reflects the common view of the late 17th century in referring to the heliocentric system as “the system of Philolaus and Copernicus” (Heninger 1974, 129–130), although in the Philolaic system it is, in fact, a central fire and not the sun that is at the center of the universe.