  The main purpose of this article is to try to understand the connection
between the physical universe and the mathematical principles that underlies
the cosmological account of the Timaeus. Aristotle's common criticism of
Plato's cosmology is that he confuses mathematical and physical constructions.
Namely, the Timaeus is the first cosmology founded on mathematical physics. We
give a new translation of Timaeus 31b-32b, an important passage to understand
the connection between mathematics and physics in Timaeus' cosmological
construction. This article is the first of a series about the kh{\^o}ra. We
will restrict our focus here to the much-debated question of the primary
elements in the kh{\^o}ra, the components of the whole physical world reduced,
in an extraordinary elegant construction, to two right triangles.
