1 The Birth of Science - MSRI

11.7 Newton’s Natural Philosophy 329
ple Arabic manuscripts, was finally prepared by Edmund Halley, 132a the
friend of Newton’s to whom we owe the discovery (or rediscovery) of periodic
comets and their elliptic orbits, not to mention the completion of page 404
the secular observational experiment designed and set in motion by Hipparchus.
134 The eighth book was never found; we have an inkling of its
contents thanks to a remark contained in the seventh. 135
That the bits of gravitational theory recorded by literary men such as
Plutarch and Seneca are only qualitative does not mean that Hipparchus
and other mathematicians of the second century B.C. necessarily neglected
the theory’s quantitative aspects. If they developed them, it would likely
have been in a direction not too far from that which Newton, based on indirect
and partial knowledge of Apollonius, later took. For we should not
forget that the gravitational theory whose partial outlines we have tried to
reconstruct came into being a few decades after Apollonius’ time, within
the same scientific tradition, and that some Hellenistic astronomers did
discover that comets are no more and no less than planets. 135a It is true that
Ptolemy never uses conics in astronomy, but he also avoids any discussion
of comets in the Almagest and he overlooks, in the Optics, the applicability
of the theory of conics to mirrors, though such applications had been
known and used systematically from the time of Dositheus (third century
B.C.) down to the Arabs. 136
Newton’s work is explicitly founded on all the prerequisites we have
listed. If the universal theory of gravitational soon managed to reach the
status of a scientific theory, despite the obvious frailty of its foundations, page 405
the reason, one suspects, is that the mutual coherence of its contributing
elements was ensured by their common origin. The starkly Aristotelian
statements made from the beginning of the Principia and onwards could
not, for instance, spoil the proofs about conics carried out according to the
Apollonian model. But it is not hard to imagine what kind of a natural
philosophy would come out of Newton’s ideas of space, time and force
in the absence of all the elements listed earlier: we have over a million
words in his pen to show us the directions he might have gone into. Newton’s
world view and methodology are easier to recognize today, thanks
to an increasing awareness of his total written output. The cardboard image
of a purely rational genius held sway for centuries because of general
ignorance of a large fraction of his writings. When these writings started
132a
Apollonii Pergaei conicorum libri octo et Sereni Antissensis de sectione cylindri et coni, Oxford, 1710.
134
See page 80.
135
See page 176, note 91.
135a
See the passages cited in Section 10.10.
136
Many other aspects of Hellenistic knowledge seem to have been unknown to Ptolemy, as we
have seen in Sections 10.4 and 10.10.
Revision: 1.11 Date: 2003/01/06 07:48:20