P: PHU/IrP
c CUNYB/Clarke December, :
The Principles of Philosophy() and ‘nothing’ does not have any measurable size (II,). This would later
provide a basis for common cause between the Jesuit Father No ̈el and
Descartes against Blaise Pascal.
Descartes uses the opportunity provided by publication of thePrinci-
plesto reveal, for the first time, three ‘laws of nature’ that he had already
formulated (in a slightly different way) inThe World.The three laws are
proposed as the fundamental principles that explain all natural phenom-
ena in terms of the motions and interactions of various parts of matter that
swirl around in an atmosphere that is filled with matter. The motion of any
particular body (i.e., a part of matter that, at least temporarily, moves with-
out joining with other parts or shedding any parts from itself ) is therefore
similar to that of a fish swimming in water. The motion of the fish does
not presuppose any empty place into which it moves, or any empty space
left in its wake after its departure. Rather, by the force of its own motion,
it displaces water that, in turn, displaces other matter that fills the space
left unoccupied by the moving fish. Descartes further developed the three
laws into seven rules that help determine what happens when, in idealized
conditions, one body collides with another. Some of the rules appear to
be counterfactual, although Descartes tries to explain away this impres-
sion by arguing that, in the real world, all bodies constantly interact with
an indeterminate number of others in their immediate environment and,
therefore, no actual collisions occur in the idealized conditions envisaged
bythe rules.
Having outlined the extremely parsimonious list of items that would
be acceptable in a Cartesian theory of the natural world – parts of matter
of varying sizes and shapes, moving with more or less speed in differ-
ent directions – and, by implication, the kinds of reality that would not
be acceptable, such as scholastic forms, qualities, and anything that was
equivalently ‘occult’ or poorly understood, Descartes aspired to explain
all natural phenomena by reference to these few items and the three laws
of nature. The concluding paragraph of Part II gives the following pro-
grammatic statement of his intentions:I freely acknowledge that I know of no matter in bodily things apart from that which
can be divided, shaped, and moved in every way....Iconsider nothing in that matter
apart from those divisions, shapes and motions....And since all natural phenomena
can be explained in this way, as will appear in what follows, I do not think that any
other principles of physics should be accepted or even desired. (II,)