Galilei, Galileo, The systems of the world, 1661

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1dicular, unleſs we firſt know that the Earth ſtands ſtill? Therefore
in your Syllogiſm the certainty of the middle term is aſſumed
from the uncertainty of the concluſion.
You may ſee then, what
and how great the Paralogiſm is.
SAGR. I would, in favour of Simplicius, defend Ariſtotle if it
were poſſible, or at leaſt better ſatisfie my ſelf concerning the
ſtrength of your illation.
You ſay, that the ſeeing the ſtone rake
along the Tower, is not ſufficient to aſſure us, that its motion is
perpendicular (which is the middle term of the Syllogiſm) unleſs
it be preſuppoſed, that the Earth ſtandeth ſtill, which is the
cluſion to be proved: For that if the Tower did move together
with the Earth, and the ſtone did ſlide along the ſame, the motion
of the ſtone would be tranſverſe, and not perpendicular.
But I
ſhall anſwer, that ſhould the Tower move, it would be impoſſible
that the ſtone ſhould fall gliding along the ſide of it; and
fore from its falling in that manner the ſtability of the Earth is
ferred.
SIMPL. It is ſo; for if you would have the ſtone in
ing to grate upon the Tower, though it were carried round by
the Earth, you muſt allow the ſtone two natural motions, to wit,
the ſtraight motion towards the Centre, and the circular about
the Centre, the which is impoſſible.
SALV. Ariſtotles defenſe then conſiſteth in the impoſſibilitie,
or at leaſt in his eſteeming it an impoſſibility, that the ſtone ſhould
move with a motion mixt of right and circular: for if he did
not hold it impoſſible that the ſtone could move to the Centre,
and about the Centre at once, he muſt have underſtood, that it
might come to paſs that the cadent ſtone might in its deſcent, race
the Tower as well when it moved as when it ſtood ſtill; and
ſequently he muſt have perceived, that from this grating nothing
could be inferred touching the mobility or immobility of the
Earth.
But this doth not any way excuſe Aristotle; aſwell
cauſe he ought to have expreſt it, if he had had ſuch a conceit, it
being ſo material a part of his Argument; as alſo becauſe it can
neither be ſaid that ſuch an effect is impoſſible, nor that Ariſtotle
did eſteem it ſo.
The firſt cannot be affirmed, for that by and
by I ſhall ſhew that it is not onely poſſible, but neceſſary: nor

much leſs can the ſecond be averred, for that Ariſtotle himſelf
granteth fire to move naturally upwards in a right line, and to
move about with the diurnal motion, imparted by Heaven to the
whole Element of Fire, and the greater part of the Air: If
fore he held it not impoſſible to mix the right motion upwards,
with the circular communicated to the Fire and Air from the
cave of the Moon, much leſs ought he to account impoſſible the
mixture of the right motion downwards of the ſtone, with the

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