"While knowledge of the dimensions of the universe had... advanced, philosophers found it... difficult to agree with regard to the physical constitution of... heavenly bodies, though all acknowledged that they were of a fiery nature, the Stoics in... supposing them... of... pure fire or ether, which pervaded... upper regions of space. ...[T]he peculiar appearance of the "face of the moon" pointed to its being... different... and... Anaxagoras and Demokritus... recognized... it was a solid mass having mountains and plains, while Plato held it to be chiefly... earthlike matter. ...[In] Plutarch "On the face in the disc of the moon"... opinion of the Stoics [that the moon is a mixture of air and gentle fire] is refuted, since the moon ought not... be invisible at new moon if it did not borrow all its light from the sun; and this... proves... it is not... a substance like glass or crystal, since s would... be impossible. The manner in which the sunlight is reflected... and... absence of a bright, reflected image of the sun and... earth, prove... the substance of the moon is not polished but is like... earth. ...Plutarch ...to combat the idea that the moon cannot be like the earth since it is not in the lowest place ...asserts ...it is not proved ...earth is in the centre of the universe, as space is infinite and therefore has no centre; ...if everything heavy and earthy were crowded together ...we should expect all ...fiery bodies ...likewise brought together."