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

its specific place and fire moves by nature to another place, and equally
so the intermediary bodies. And the world is only finite, because of the
spherical body, and this because of the essential and natural finiteness of
the spherical body, as one single plane circumscribes it.’ Rectilinear
bodies are not essentially finite, as they allow of an increase and
decrease; they are only finite because they are in the middle of a body
that admits neither increase nor decrease, and is therefore essentially
finite. And, therefore, the body circumscribing the world cannot but be
spherical, as otherwise the bodies would either have to end in other
bodies, and we should have an infinite regress, or they would end in
empty space, and the impossibility of both suppositions has been
demonstrated. He who understands this knows that every possible world
imaginable can only consist of these bodies, and that bodies have to be
either circular-and then they are neither heavy nor light-or rectilinear-and
then they are either heavy or light, i.e. either fire or earth or the
intermediate bodies; that these bodies have to be either revolving, or
surrounded by a revolving periphery, for each body either moves from,
towards, or round the centre; that by the movements of the heavenly
bodies to the right and to the left all bodies are constituted and all that is
produced from opposites is generated; and that through these movements
the individuals of these four bodies never cease being in a continual
production and corruption. Indeed, if a single one of these movements
should cease, the order and proportion of this universe would disappear,
for it is clear that this order must necessarily depend on the actual number
of these movements-for if this were smaller or greater, either the order
would be disturbed, or there would be another order-and that the number
of these movements is as it is, either through its necessity for the
existence of this sublunary world, or because it is the best .
Do not ask here for a proof for all this, but if you are interested in
science, look for its proof, where you can find it. Here, however, listen to
theories which are more convincing than those of the theologians and
which, even if they do not bring you complete proof, will give your mind an
inclination to lead you to proof through scientific speculation. You should
imagine that each heavenly sphere is a living being, in so far as it
possesses a body of a definite measure and shape and moves itself in
definite directions, not at random. Anything of this nature is necessarily a
living being; i.e. when we see a body of a definite quality and quantity
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