1 The Birth of Science - MSRI

1.4 Was There “Science” in Classical Greece? 19
Without reconstructing all of Aristotle’s reasoning, we focus on certain
key features of the method he uses to approach the problem of movement
(and other “physics” questions, for that matter). Aristotle’s problem
is determining the quantitative relationship between force, time, and displacement.
With the scientific method one can solve such problems in one page 43
of two ways: either by supposing a relation given “in principle” (in which
case experiment plays an essential role in checking whether the real phenomena
whose model one wishes to build do in fact occur in the way
predicted by applying the correspondence rules to the stated principle),
or else by deducing the desired relationship inside a preexisting scientific
theory, using the deductive method. Aristotle, however, cannot use either
the deductive method or experiments, because he does not have, and does
not wish to build, a scientific theory. The forces, times and displacements
that he talks about are not in fact entities internal to a theory, but he conceives
them as concrete objects, whose mutual relations can be understood
via philosophical speculation.
He mentions an empirical datum (the impossibility of a single person
moving a ship), but the decisive argument is that the portion of the force
under consideration acts differently depending on whether it is in isolation
or as part of a whole, because in the second case the part exists potentially
only. Thus the empirical fact is mentioned just by way of illustration,
for all intents and purposes. The real game is to deduce quantitative statements
about particular physical phenomena directly from general philosophical
principles, derived from qualitative observations of nature.
Archimedes’ confutation of Aristotle’s argument, reported by Plutarch
and Proclus, was very persuasive. According to the tradition they transmit,
Archimedes designed, within his scientific theory of mechanics, a
device that enabled a single man — himself or King Hiero II, depending
on the version — to drag into the water a ship towed up onto dry land
in the Syracuse harbor; Proclus specifies it was a full-laden three-masted
ship. 39 The machine itself carried out the division of force that Aristotle
had judged impossible, and which indeed had probably never been
achieved before for a ship. This was a very effective way to demonstrate page 44
the superiority of “scientific” method, in the sense already explained, over
natural philosophy. Rather than reflecting the world in philosophical speculation,
the scientific method had changed the world, by allowing the design
of a machine that eliminated the impossibility observed by Aristotle.
The methodological value of the experimental demonstration narrated
by Proclus and Plutarch, which stands out most clearly in comparison
39 [Proclus/Friedlein], p. 63. The same episode is told by Plutarch in a slightly different way
(Plutarch, Vita Marcelli, xiv, 8).
Revision: 1.15 Date: 2002/09/12 02:47:10