1 The Birth of Science - MSRI

11.8 The Rift Between Mathematics and Physics 335
The assertion is blatantly and intentionally “false”. Stevin obviously plans
to build a model based on a simplification of reality, and he does not think
that postulates must be “true”. This short work (containing no formulas
or quantitative arguments of any sort) was published in 1608 as part of
his Wisconstighe ghedachtenissen, or Mathematical works, precisely because
of its logical structure and the role played in it by postulates such as the
one quoted.
The term “physics”, too, had until the seventeenth century a sense similar
to the Greek one: it was used for works in natural philosophy, or in the
medical and biological sciences, while the practitioners of exact science
called themselves mathematicians, when not philosophers.
We have seen that Galileo did not hesitate in ranking his “new science”
of motion under gravity together with the scientific tradition of Euclid,
Archimedes and Apollonius. 151
But the ancient method was understood by very few of Galileo’s contemporaries.
It had not been utterly forgotten, but few scientists felt free
(as Stevin did) to choose hypotheses for building models; much more page 411
frequently, the arbitrariness involved in setting ground assumptions was
taken (as it had by Simplicius and Thomas Aquinas) as a quirk of mathematicians
and a sign of the weakness of the mathematical method as
compared to philosophy and theology, which could tell right from wrong.
Here, for example, is a letter of April 12, 1615, from Cardinal Bellarmino
to Brother P. A. Foscarini, who had tried to reconcile heliocentrism with
Scripture:
It seems to me that you, Father, and Mr. Galileo act prudently in
staying with arguments ex suppositione rather than speaking absolutely.
. . . For saying that, supposing that the earth moves and the
sun is fixed, all appearances are saved better than with eccentrics
and epicycles, is very well and involves no danger, and is enough for
mathematicians: but wanting to claim that the sun really is at the center
of the world and just turns around itself without speeding from
east to west, and that the earth lies in the third heaven and turns with
enormous speed around the sun, is a very dangerous thing, capable
not only of annoying all philosophers and scholastic theologians, but
also of injuring the Holy Faith by belying the Sacred Scriptures. 152
As is well known, Bellarmino’s recommendation was in part adopted by
Galileo himself, though only as a ruse to try to avoid censure and condemnation.
151 See the quote on page 307.
152 This letter appears in [Galileo: Opere], vol. XII, pp. 171–172.
Revision: 1.11 Date: 2003/01/06 07:48:20