The Aristotelian world system.
Natural philosophy was dominated
for nearly two millennia by the ideas of Aristotle,
which were then reinterpreted by the Scholastics in order to bring
them into line with the dogmas of the Christian faith.
In his Physics, Aristotle declares that
the affirmation of the existence of the void - as Democritus
had done - represented an infringement of the principle of non-contradiction.
For Aristotle, a space without objects (that is, void), is not in
fact the same as nothing, but has its own permanent existence.
Nor can the void, for Aristotle, be considered insofar as it is immaterial,
seeing that natural philosophy has as its object only being as being.
On the other hand, Aristotle, while conceiving of the universe as
finite, denied resolutely that beyond the confines of the world there
was the void.
The Greek philosopher, moreover, considered the sublunar world to
be composed of four elements (fire, air, earth and water) and claimed
that each of these had its own natural place, from which it could
be removed only by an act of violence. In their natural places, elements
did not have weight. So air, for the Greek philosopher and his many
followers, had no weight, and did not exert pressure.