  The Martianus commentary is most famous for its apparent espousal of a non-Ptolemaic account of the movement of the planets in Book Seven on astronomy. Pierre Duhem (1958) thought that Eriugena was offering a version of the system later proposed by Tycho Brahe, and in fact Eriugena is correctly reporting Martianus’ account which seems to be a version of Heraclides of Pontus’ theory. Indeed, Copernicus would later single out Martianus for praise for his theory that Mercury and Venus orbit the sun instead of the earth. Eriugena went further than Martianus in placing Mars and Jupiter in orbit around the sun also.