Galilei, Galileo Dialogues on two world systems 1661, tr. Salusbury, Thomas
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24
that to move towards this, is a moving towards that of the World,
that he cannot affirm, unless he supposeth, That the Centre of the

Earth, from which we see these light ascendent bodies to depart,
be the same with the Centre of the World; which is as much as
to say, that the terrestrial Globe is constituted in the midst of the
World: which is yet that of which we were in doubt, and which
Aristotle intended to prove. And do you say that this is not a

manifest Paralogism?

* A famous Italian
Painter.

Paralogism of A­
ristotle, in proving
the Earth to be in
the Centre of the
World.

The Paralogisme
of Aristotle another
way discovered.

SAGR. This Argument of Aristotle appeared to me deficient
also, and non-concludent for another respect; though it were
granted, that that Circumference, to which the Fire directly mo­
veth, be that which includeth the World: for that in a circle,
not onely the centre, but any other point being taken, every move­
able which departing thence, shall move in a right line, and to­
wards any whatsoever part, shall without any doubt go towards
the circumference, and continuing the motion, shall also arrive
thither; so that we may truly say, that it moveth towards the
circumference: but yet it doth not follow, that that which mo­
veth by the same line with a contrary motion, would go towards
the centre, unless when the point taken were the centre it self,
or that the motion were made by that onely line, which produced
from the point assigned, passeth thorow the centre. So that to
say, that Fire moving in a right line, goeth towards the circumfe­
rence of the World, therefore the parts of the Earth which by
the same lines move with a contrary motion, go towards the cen­
tre of the World, concludeth not, unless then when it is pre­
supposed, that the lines of the Fire prolonged pass by the centre
of the World; and because we know certainly of them, that they
pass by the centre of the Terrestrial Globe (being perpendicu­
lar to its superficies, and not inclined) therefore to conclude, it
must be supposed, that the centre of the Earth is the same with
the centre of the World; or at least, that the parts of the Fire
and Earth descend not, save onely by one sole line which passeth
by the centre of the World. Which nevertheless is false, and re­
pugnant to experience, which sheweth us, that the parts of
Fire, not by one line onely, but by infinite, produced from the
centre of the Earth towards all the parts of the World, ascend
always by lines perpendicular to the Superficies of the Terrestri­
al Globe.

SALV. You do very ingeniously lead Aristotle to the same in­
convenience, Sagredus, shewing his manifest equivoke; but
withal you add another inconsistency. We see the Earth to be
spherical, and therefore are certain that it hath its centre, to which
we see all its parts are moved; for so we must say, whilst their
motions are all perpendicular to the Superficies of the Earth; we