Aristotle was the first to really attempt to prove that the Earth was spherical. It is a topic he discusses in
great detail in book II of his work On the Heavens, engaging with the various arguments that preceded him,
using philosophical arguments and observations of the natural world (On the Heavens [written in 350 BC], 2.14):
How else would eclipses of the moon show segments shaped as we see them? As it is, the shapes
which the moon itself each month shows are of every kind straight, gibbous, and concave-but in
eclipses the outline is always curved: and, since it is the interposition of the earth that makes the
eclipse, the form of this line will be caused by the form of the earth’s surface, which is therefore
spherical. Again, our observations of the stars make it evident, not only that the earth is circular,
but also that it is a circle of no great size. By the end of the fourth century BC, the idea of a spherical
world was more common place than any other answer – and Aristotle’s work, in particular, would
strongly influence scholastic views on this question right through ancient and medieval Europe.