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.