Arnauld attacked Leibniz for reintroducing the notion of substantial
form. The Jansenist Pascal rejected Aristotelianism; his important experiments with a
barometer were partly intended to refute the Aristotelian denial of the existence of a
vacuum. The rejection of Aristotelianism was part of what appealed to the Oratory and the
Jansenists about the mechanical philosophy. As extreme Augustinians, they disliked the
influence of Aristotle on Catholic theology, which they believed tended to promote an
excessively liberal conception of the freedom of the human will.