LXXVIII. Finally, there is no motion whatever, about the cause of which,
the philosophers do not altercate. What contests have there been among
them, to explain how the movements of rarefaction, and condensation are
performed? Some fancy, that rarefaction consists, in the same quantity
of matter occupying a larger space; which explanation, others looking
upon as unintelligible, assert, it consists in the opening of the pores,
and the extension in consequence of that opening, of various parts of
the body, by the introduction of a subtil liquid substance, in the same
manner that water enters a spunge, or as rarefied air enters water,
or the ætherial matter insinuates itself into the air. This is the
doctrine of the Cartesians; but in the opinion of the Maignanists, and
Gassendists, such reasoning is nothing to the purpose; for these, as
they admit in nature, not only of the possibility, but of the necessity
of a vacuum, or many voids distributed in small interstices, find no
inconvenience in supposing, that in bodies, there are small empty spaces,
unpossessed by any matter whatever.
LXXIX. Fermentation, this solemn instrument of nature for the performance
of an infinite number of her works; consists in nothing, but an
intestine motion of the insensible particles of the mixtures, by which
is solicited, a new combination of their elements. But from whence does
this motion proceed? The Moderns, since the discovery of the acid and the
alkali by Otho Takenius, attribute all the fermentations, to the meeting
of these two substances. But this is only pointing out the matter, on
which this motion has its effect, and we do not enquire here for the
material cause, but for the efficient one. Who, or what, impels the acid
and the alkali to this conflict? The juice newly expressed from the
grape, will quiet this combustion for some little time; but after that,
the tumult begins again. What new agent can we discover here, to excite
the second fermentation? This is a secret, which only the Cartesians have
presumed to unravel, by recurring to their invisible fairy, _the subtil
matter_; whom they make the author of all this domestic sedition. It is
with some propriety that I call it a fairy; for as the vulgar attribute
to the fairies, all the nocturnal noises and commotions, whose causes
they are ignorant of; so the Cartesians impute all those motions, which
on account of the darkness that obscures their causes, may be truly
termed nocturnal, to the impulse of the subtil matter.
LXXX. I am so far from believing, that the subtil matter is the _primum
mobile_, or first mover of every thing, that I am inclined to think, it
moves nothing. My reason for this opinion, is as follows. The more fluid
a matter is, so much the less impulse it makes on any body it encounters.
Thus we see, that water gives a much less violent shock to a wall, than
any other solid body of equal size, that may be forcibly driven against
it; and air, a much less than water. No building could stand against, or
resist a moderate gale of wind, if the air was as solid as water. The
subtil matter then, according to the doctrine of the Cartesians, being
infinitely fluid, can have but little impulse, or be able to impress but
little agitation or motion, on the bodies it encounters. This consequence
to me, is clear and plain; because, if in proportion to the augmentation
of its fluidity, the impulse of a body is lessened, when the fluidity
comes to be infinite, the impulse will cease totally. From hence it would
follow, that there is no body whatever, which could be moved by the
impulse of the subtil matter.
LXXXI. But admitting that it has power, as the Cartesians pretend, to
move the insensible particles of the mixtures; it will not follow
from thence, that it furnishes us with an explanation of the present
phenomenon. For in the first place, the subtil matter, if it has any
impulse, exercises it on the particles of the juice the instant that
it is pressed from the grape; and even perhaps did it before, while
the liquor was contained within the outside skin or covering. How then
does it happen, that it did not sooner excite that tumult, which is the
symptom and property of fermentation? Secondly, how can the acids and
alkalies be said to produce this effect? for, according to the doctrine
of the Cartesians, of whatever particles the mixtures consist, the subtil
matter would set them in motion, for that there is no mixture whatever,
impenetrable to its extreme subtilty. Thirdly, how can those exceeding
slow fermentations, which are years before they manifest themselves, as
in the instance of treacle, be attributed to the rapid and swift motion
of the subtil matter?