1) Special connections exist between a body's location in space and its natural motion. Movements in the sublunar region are naturally vertical. Movements in the celestial region are natural spherically.

2) Special connections exist between a body's location and its nature. In the sub lunar region bodies can change due to generation and corruption. These bodies are composed of 4 elements and contain opposite qualities ( hot, cold), (wet, dry). Bodies in the celestial region are composed of a special element, quintessence, or celestial matter. Celestial matter is eternal and unchangeable. There is a very close connection between the nature of the substance and its motion. The circular motion was stated to be eternal and this is natural motion for an eternal object.

MODERN VALUE OF DE CAELO ?

(From a commentary by  Leo Elders )

1) De caelo is the first treatise on cosmology in which the approach is purely scientific.
" The De caelo is, indeed, an attempt to explain by means of arguments stripped of poetical ornaments and images, the nature, shape and eternity of the universe; the main parts of the world are distinguished the one from the other and analyzed. ...(it) is a landmark in the history of natural philosophy."

2) " The De caelo is characterized by the spirit of its time, and shows the defects of it: too simple a view of the universe and overconfidence in certain general sense impressions as a basis for inference."

Strengths of De caelo
- " ... the conviction that the outside world can be understood rationally."

-" ... the principles of thought do apply to the structure of reality." ( can include the use of mathematical modeling)

-"" ... the use of one schematic image of the universe, by
means of which all the available facts of experience are explained."

There are several other conceptual parallels that Elders draws between Aristotle's thinking and modern physics.

• Universe occupies a limited volume.
• Universe is a closed system( total energy is constant)
• Revolution of  a body inherent in its nature( spin)
• Behavior and composition of matter in specific zones of the world depends on conditions in that zone.

' ...progress in science is to be measured not by the questions which seem to have received an answer, but by the questions that it provokes us to ask.'
(A. Eddington, New Pathways in Science , Cambridge 1935, p.325)

Is Aristotle outmoded? (Pay back for Simplicio !)

" ...we cannot help, to a great extent, being Aristotelians for the great Master does but analyze the thoughts, feelings, views and opinions of human kind. He has told us the meaning of our own words and ideas before we were born. In many subject matters to think correctly is to think like Aristotle; and we are his disciples whether we will or not, though we may not know it."

from J. H. Newman in The Idea of a University , New York, 1947, p.97

Source for commentary
Aristotle's Cosmology: A commentary on the De caelo
Leo Elders S.V.D., Ph.D., Van Gorcum and Comp., Netherlands, 1965