are mutable. But if there were any body immortal,
then all bodies would not be mutable. Every body, then, is mortal; for
every body is either water, air, fire, or earth, or composed of the
four elements together, or of some of them. Now, there is not one of
all these elements that does not perish; for earthly bodies are
fragile: water is so soft that the least shock will separate its parts,
and fire and air yield to the least impulse, and are subject to
dissolution; besides, any of these elements perish when converted into
another nature, as when water is formed from earth, the air from water,
and the sky from air, and when they change in the same manner back
again. Therefore, if there is nothing but what is perishable in the
composition of all animals, there is no animal eternal.

XIII. But, not to insist on these arguments, there is no animal to be
found that had not a beginning, and will not have an end; for every
animal being sensitive, they are consequently all sensible of cold and
heat, sweet and bitter; nor can they have pleasing sensations without
being subject to the contrary. As, therefore, they receive pleasure,
they likewise receive pain; and whatever being is subject to pain must
necessarily be subject to death. It must be allowed, therefore, that
every animal is mortal.

Besides, a being that is not sensible of pleasure or pain cannot have
the essence of an animal; if, then, on the one hand, every animal must
be sensible of pleasure and pain, and if, on the other, every being
that has these sensations cannot be immortal, we may conclude that as
there is no animal insensible, there is none immortal. Besides, there
is no animal without inclination and aversion--an inclination to that
which is agreeable to nature, and an aversion to the contrary: there
are in the case of every animal some things which they covet, and
others they reject. What they reject are repugnant to their nature, and
consequently would destroy them. Every animal, therefore, is inevitably
subject to be destroyed. There are innumerable arguments to prove that
whatever is sensitive is perishable; for cold, heat, pleasure, pain,
and all that affects the sense, when they become excessive, cause
destruction. Since, then, there is no animal that is not sensitive,
there is none immortal.

XIV. The substance of an animal is either simple or compound; simple,
if it is composed only of earth, of fire, of air, or of water (and of
such a sort of b