Tahafut_al-Tahafut-transl-Engl-van-den-Bergh

I say:
possible that the world might be bigger or smaller than it is
by a cubit, this is not the same as regarding it as possible to
identify black with white and existence with non-existence;
impossibility lies in affirming the negative and the positive at
the same time, and all impossibilities amount to this. This is
indeed a silly and faulty assertion.’
This statement is, as he says, an affront to reason, but only to the
reason of him who judges superficially; it is not an affront to true reason,
for a statement about its being possible or not’ requires a proof. And
therefore he is right when he declares that this is not impossible in the way
in which the assumption that black might be white is impossible, for the
impossibility of the latter is self-evident. The statement, however, that the
world could not be smaller or larger than it is is not self-evident. And
although all impossibilities can be reduced to self-evident impossibilities,
this reduction can take place in two ways. The first is that the impossibility
is self-evident; the second is that there follows sooner or later from its
supposition an impossibility of the same character as that of self-evident
impossibilities.’ For instance, if it is assumed that the world might be larger
or smaller than it is, it follows that outside it there would be occupied or
empty space. And from the supposition that there is outside it occupied or
empty space, some of the greatest impossibilities follow: from empty
space the existence of mere extension existing by itself; from occupied
space a body moving either upward or downward or in a circle which
therefore must be part of another world. Now it has been proved in the
science of physics that the existence of another world at the same time as
this is an impossibility and the most unlikely consequence would be that
the world should have empty space: for any world must needs have four
elements and a spherical body revolving round them. He who wants to
ascertain this should look up the places where its exposition is demandedthis,
of course, after having fulfilled the preliminary conditions necessary
for the student to understand strict proof .
Then Ghazali mentions the second reason:
If the world is in the state it is, without the possibility of
being larger or smaller than it is, then its existence, as it is, is
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