Reference:  G. J. Toomer, Ptolemy's ALMAGEST ,
Springer-Verlag, New York, Heidelberg, Tokyo, 1984
  Ptolemy (AD 100 - AD 170)

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

• theology, dealing with the "first cause" of motion which is somewhere in the highest reaches of the universe and can only be imagined
• physics, dealing with matter and motion. Such an order of being is situated below the lunar sphere among corruptible bodies.
• mathematics, dealing with form, motion, shape, number, place, time, etc. Joins the first two areas because mathematics is an attribute of all existing things, mortal and immortal( i.e. of an aethereal nature, things beyond the lunar sphere)

"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 heavens move like a sphere - "nature formed all earthly and corruptible bodies out of shapes which are round but of unlike parts, but all aethereal and divine bodies out of shapes which are of like parts and spherical. ... it is plausible that the aether surrounding them, too, being of the same nature, is spherical, and because of the likeness of its parts moves in a circular and uniform fashion."
• the earth is spherical
• the earth is in the middle of the heavens
• the earth is negligibly small compared to the heavens
• the earth does not have any motion from place to place (because of various physical arguments) nor does it rotate in a fixed place ( for example clouds and projectiles would never be seen moving towards the east, the earth's rotation would always overtake them)