Natural Philosophy 191ematicians during the seventeenth century and several—Roger Boscovich,
Girolamo Saccheri, and Leonardo Ximenes, among others—in the eigh-
teenth.^47 The Jesuits gave an important place to applied mathematics in
their curriculum for this- worldly reasons. Mathematics attracted sons of
elite families, who might need to know something about calculation, ar-
chitecture, surveying, and fortifi cation, as well as fencing and dancing
(which were also taught in Jesuit schools), for their future roles in society.
Secondly, as a means of teaching controversial and even condemned sub-
jects, especially Copernican astronomy, mathematics was magic. The Jesu-
its turned Aristotle’s doctrine that mathematics offers an exact description
of phenomena, but no demonstration of the truth, into an argument for
presenting astronomical systems as harmless but useful hypotheses. Their
pedagogical mission reinforced their Jesuitical epistemology: especially in
the eighteenth century, when they began to lose market share to other
teaching orders, they had to keep their curriculum up- to- date. Thus the
Jesuits tended to multiply mathematicians, many of whom, including
members of the society, found niches in which to contribute to natural
philosophy outside the order’s institutions.
Two examples will indicate the possibilities. Boscovich began his ex-
traordinarily varied career as a professor of mathematics at the Jesuits’
main seminary, the Gregorian College in Rome. Then, acting as a civil
engineer, he drew up plans for repairing St Peter’s, canalizing the Tiber,
and building harbors. On order from the Vatican, he made a trigonomet-
ric survey of the Papal States. He taught mathematics at the Jesuit college
in Pavia and founded the Jesuit observatory in Milan. He became, briefl y,
director of optics for the French Navy. He was a member of the Paris Acad-
emy and the Royal Society. Ximenes learned enough mathematics at the
Gregorian College to be sent by his general as tutor in the subject to the
family of a Florentine duke. He also wrote some mathematics, published
an almanac, and made a small name for himself. That was enough to
bring him an ill- paying job as professor of mathematics at the Univer-
sity of Florence and many commissions from local governments to drain
swamps, manage wetlands, canalize rivers, and repair buildings. For a year
or so he turned the cathedral of Florence into a laboratory of experimental
physics and a solar observatory in order to answer the then vexed ques-
tion whether the inclination of Earth’s axis changes slowly in time.^48
The history of the Jesuits agrees with that of natural philosophy in
suffering a sea change around 1770. Their expulsion from several Euro-
pean states in the 1760s and their suppression by the pope in 1773 freed
governments from the meddling of the society at the cost of a rich source
of teachers, informers, and disciplinarians. The well- organized Jesuits fell