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

the immediately evident axioms; and it is explained in the Posterior
Analytics of what kind these premisses area
Ghazali says:
I say:
The second objection is that, if it were conceded to Galen
that there is no corruption except through decay, how can it
be known that decay does not affect the sun? His reliance
on observation is impossible, for observations determine the
size only by approximation, and if the sun, whose size is said
to be approximately a hundred and seventy times that of the
earth, decreased, for instance, by the size of mountains the
difference would not be perceptible to the senses. Indeed, it
is perhaps already in decay, and has decreased up to the
present by the size of mountains or more; but perception
cannot ascertain this, for its knowledge in the science of
optics works only by supposition and approximation. The
same takes place with sapphire and gold, which, according
to them, are composed out of elements and which are liable
to corruption. Still, if you left a sapphire for a hundred years,
its decrease would be imperceptible, and perhaps the
decrease in the sun during the period in which it has been
observed stands in proportion to its size as the decrease of
the sapphire to its size in a hundred years. This is
imperceptible, and this fact shows that his proof is utterly
futile.
We have abstained from bringing many proofs of the
same kind as the wise disdain. We have given only this one
to serve as an example of what we have omitted, and the
have restricted ourselves to the four proofs which demand
that their solution should be attempted in the way indicated
above.
If the sun had decayed and the parts of it which had disintegrated
during the period of its observation were imperceptible because of the size
of its body, still the effect of its decay on bodies in the sublunary world
would be perceptible in a definite degree, for everything that decays does
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