Wrestling with Nature From Omens to Science

Natural Knowledge in the Classical World 45

collection and organization of massive amounts of data (his own and the
work of previous researchers, going back as far as the historical record
permitted and across several languages), and the use and further develop-
ment of very sophisticated and highly accurate mathematical modeling
based on that data. This is a different kind of project than the one Aristotle
was engaged in. Unfortunately, we know next to nothing about Ptolemy’s
life, and so we are not in a position to speculate with any certainty on
who, if anyone, patronized his work, what the institutional context was,
and so on. But we are lucky enough to have his own account of the intel-
lectual justifi cation for his work, and he paints an interesting picture.
For Ptolemy, the glorious thing about mathematical sciences was their
certainty. Of course, any ancient mathematician would agree: mathemat-
ics was the very paradigm of certainty in antiquity, and other sciences
sometimes looked to it as a model. Galen, for example, consciously tried
to model his medical and physiological arguments and demonstrations
on geometrical proofs. But he did this in a formal sense, using the logi-
cal tools and structures of geometrical demonstration, rather than in the
literal sense of applying rulers and compasses to the human body. But
Ptolemy actually went this one step further to explore the point where
mathematics meets the physical world. Here is what he had to say about
the certainty this offers:

Hence we thought it fi tting... to devote most of our time to intellectual mat-

ters, to teach especially those theories—many and beautiful that they are—to

which the name “mathematical” is particularly applied. For Aristotle divides

theoretical philosophy very fi ttingly into three primary categories: physics,

mathematics, and theology... Now the fi rst cause of the fi rst motion in the

universe, if one considers it plainly, can be thought of as an invisible and

motionless god. The division [of philosophy] concerned with investigating

this is theology, and up in the highest reaches of the Cosmos, it can only be

examined by thought... The division that investigates material and ever-

changing nature... one may call “physics” and its realm is situated for the

most part amongst the corruptible bodies below the lunar sphere.^18

So theology’s object of study is so remote as to be only accessible in the
mind, and the object of the study of physics is inherently corruptible and
always changing. Neither of them, then, can provide certainty: “theology
because of its completely invisible and ungraspable nature, and physics
because of the unstable and unclear nature of matter.”^19 In comparison
to mathematics, these two branches of philosophy pale to such an extent
that Ptolemy called them “guesswork.” He despaired: “there is no hope