PTOLEMY'S COSMOLOGY

Reference:  G. J. Toomer, Ptolemy's ALMAGEST ,
Springer-Verlag, New York, Heidelberg, Tokyo, 1984
 

In the preface of Book I Ptolemy divides theoretical philosophy into three parts

The heavenly bodies are referred to as being eternal. Mathematics spans the other two fields of theoretical philosophy.

"As for physics, mathematics can make a significant contribution. For almost every peculiar attribute of material nature becomes apparent from the peculiarities of its motion from place to place. Thus one can distinguish the corruptible from the incorruptible by whether it undergoes motion in a straight line or a circle, and heavy from light, and passive from active, be whether it moves towards the centre or away from the centre." ( p.36)

Ptolemy summarizes the ideas and reasons for the current world picture.

The rest of his book deals with mathematical techniques for computing the positions of the stars and planets.