The central fire received a number of mythological names. It was called the Hestia or “hearth of the universe,” the “house” or “watch-tower” of Zeus, and the “mother of the gods.”[827] That was in the manner of the school; but these names must not blind us to the fact that we are dealing with a real scientific hypothesis. It was a great thing to see that the phenomena could best be “saved” by a central luminary, and that the earth must therefore be a revolving sphere like the planets. Indeed, we are almost tempted to say that the identification of the central fire with the sun, which was suggested for the first time in the Academy, is a mere detail in comparison. The great thing was that the earth should definitely take its place among the planets; for once it has done so, we can proceed to search for the true “hearth” of the planetary system at our leisure. It is probable, at any rate, that it was this theory which made it possible for Herakleides of Pontos and Aristarchos of Samos to reach the heliocentric hypothesis,[828] and it was certainly Aristotle’s reversion to the geocentric theory which made it necessary for Copernicus to discover the truth afresh. We have his own word for it that the Pythagorean theory put him on the right track.[829] Footnote 827: Aet. i. 7, 7 (R. P. 81). Procl. _in Tim._ p. 106, 22, Diehl (R. P. 83 e). Footnote 828: On these points, see Staigmüller, _Beiträge zur Gesch. der Naturwissenschaften im klassichen Altertume_ (Progr., Stuttgart, 1899); and “Herakleides Pontikos und das heliokentrische System” (_Arch._ xv. pp. 141 sqq.). Though, for reasons which will partly appear from the following pages, I should not put the matter exactly as Staigmüller does, I have no doubt that he is substantially right. Diels had already expressed his adhesion to the view that Herakleides was the real author of the heliocentric hypothesis (_Berl. Sitzb._, 1893, P. 18). Footnote 829: In his letter to Pope Paul III., Copernicus quotes Plut. _Plac._ iii. 13, 2-3 (R. P. 83 a), and adds “Inde igitur occasionem nactus, coepi et ego de terrae mobilitate cogitare.” The whole passage is paraphrased by Dreyer, _Planetary Systems_, p. 311. Cf. also the passage from the original MS., which was first printed in the edition of 1873, translated by Dreyer, _ib._ pp. 314 sqq. [Sidenote: The _antichthon_.]