c CUNYB/Clarke December, :
Once More into Battle moods. He even claimed subsequently to have suggested the Puy-de-Domeˆ
experiment to Pascal during their meeting in September.However,
Pascal and Descartes differed about how to describe the apparently empty,
enclosed space at the top of a mercury column in a Torricelli tube. Pascal
thought it contained a vacuum, whereas Descartes had argued for at least
two decades that there is no such thing as a genuine vacuum in nature.
Descartes’ argument about the vacuum was metaphysical rather than
something he had concluded from observation or experiment. He argued
consistently throughout his career that an apparently empty space has
dimensions, and that dimensions cannot be predicated of a complete
nonentity. He had recently developed this argument in reply to Queen
Christina, arguing that the apparently empty spaces beyond the solar sys-
tem cannot be absolutely empty and that they must contain some matter.
In a similar way, the apparently empty space above a column of mercury
must contain some kind of matter, which is invisible to the naked eye but
has very specific dimensions. He was joined in this debate by an unlikely
ally, his former Jesuit teacher FatherEtienne No ́ ̈el.
No ̈el corresponded with Pascal in the autumn of,following pub-
lication of theNew Experimentsbutbefore the Puy-de-Dome experimentˆ
had been done. The fact that he was a Jesuit cannot have helped his cause
in criticizing the rather irascible Pascal. He accepted the validity of Pas-
cal’s experiments – although others doubted that he could have performed
them as described – and he agreed with him that columns of liquid are not
supported by nature’s fear of a vacuum.However, he could not see how
an absolute vacuum could have the physical properties that were observed
in the apparently empty space above the mercury.I read your experiments about the vacuum, which I find very good and ingenious, but
Idonot understand this apparent vacuum which appears in the tube after either the
water or mercury has dropped. I say that it is a body, because it acts like a body, it
transmits light with refractions and reflections, it retards the movement of another
body, which can be observed in the descent of the mercury when the tube that is filled
atthe top with this vacuum is inverted.Thus No ̈el’s arguments closely mimicked those of Descartes and were
most likely influenced by his reading of Descartes’ work. His style of
argument, however, remained more scholastic than that of his former
pupil. For example, he could not understand what kind of reality a vac-
uum was supposed to be, because it did not fall within either of the two