348 
FROM PLATO TO EUCLID 
terminating it, the indivisible line must be divisible ; and, 
lastly, various arguments are put forward to show that a line 
can no more be made up of points than of indivisible lines, 
with more about the relation of points to lines, Ac. 1 
Sphaeric. 
Autolycus of Pitane was the teacher of Arcesilaus (about 
315-241/40 B. c.), also of Pitane, the founder of the so-called 
Middle Academy. He may be taken to have flourished about 
310 B. c. or a little earlier, so that he was an elder con 
temporary of Euclid. We hear of him in connexion with 
Eudoxus’s theory of concentric spheres, to which he adhered. 
The great difficulty in the way of this theory was early seen, 
namely the impossibility of reconciling the assumption of the 
invariability of the distance of each planet with the observed 
differences in the brightness, especially of Mars and Venus, 
at different times, and the apparent differences in the relative 
sizes of the sun and moon. We are told that no one before 
Autolycus had even attempted to deal with.this difficulty 
‘ by means of hypotheses i. e,- (presumably) in a theoretical 
manner, and even he was not successful, as clearly appeared 
from his controversy with Aristotherus 2 (who was the teacher 
of Aratus) ; this implies that Autolycus’s argument was in 
a written treatise. 
Two works by Autolycus have come down to us. They 
both deal with the geometry of the sphere in its application 
to astronomy. The definite place which they held among 
Greek astronOinical text-books is attested by the fact that, as 
we gather from Pappus, one of them, the treatise On the 
moving Sphere, was included in the list of works forming 
the ‘ Little Astronomy ’, as it was called afterwards, to distin 
guish it from the ‘Great Collection’ (/leyaXg crvuragis) of 
Ptolemy ; and we may doubtless assume that the other work 
On Risings and Settings was similarly included. 
1 A revised text of the work is included in Aristotle, De plantis, edited 
by 0. Apelt, who also gave a German translation of it in Beiträge zur 
Geschichte der griechischen Philosophie (1891), pp. 271-86. A translation 
by H. H. Joachim has since appeared (1908) in the series of Oxford 
Translations of Aristotle’s works. 
2 Simplicius on De caelo, p. 504. 22-5 Heib.