Natural Philosophy 175The second section below cuts up the string of natural philosophers
into some of its better- known parts. The fi rst section breaks open the
hourglass.
THE HOURGLASS OF PHYSICS
1: Natural Philosophy
“Natural philosophy” is not- very- plain English for Latin physica and
French physique. It concerns natural knowledge. It does not carry any im-
plication of natural theology, although many natural philosophers be-
lieved that their studies of God’s handiwork brought them close to their
Creator. “Cull the sweets of religion, as you roam through the fl owery
paths of natural philosophy,” Margaret Bryan admonished the girls to
whom she taught physics, “and guard your religious and moral principles
against all innovations.” The correct term for “culling the sweets,” or (to
quote Samuel Johnson) for contemplating “divinity enforced or illustrated
by natural philosophy” was “physico- theology.”^3
To know that natural philosophy was physics and not natural theology
is not to know much. The Encyclopédie of Diderot and d’Alembert takes
us only a little further. It defi ned physique (alias philosophie naturelle) in
the manner of Aristotle and the scholastic philosophers as the “science of
the properties of [all] natural bodies, their phenomena and their effects,”
and so was marginally more restrictive than Locke’s natural philosophy,
which included the study of angels. When the Encyclopédie proffered its
defi nition in 1765, however, physics books no longer covered everything
from animalcula to the stars. Charles Hutton repeated it sixty years later
in his Philosophical and mathematical dictionary of 1815, a year before Jean
Baptiste Biot published his voluminous Traité de physique expérimentale
et mathématique, the fi rst full textbook of physics restricted to domains
and methods recognizably modern.^4 The effective meaning of physics or
natural philosophy during the eighteenth century cannot be determined
by examining dictionaries.
The title of Biot’s text suggests a periodization of natural philosophy
as well as its content in his time. First came experiment, then the combi-
nation of experiment with mathematics. That is roughly what happened
from the middle of the seventeenth century to the end of the eighteenth
in textbooks and also in real life. Jacques Rohault’s Traité de physique, a
work of Cartesian inspiration fi rst published in 1671, was exemplary for
the decades around 1700. It reached its sixth French edition in 1692 and
its third English translation, with prophylactic notes by Newton’s paladin