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 being we can form no idea); compound, if it is formed of different elements, which have each their proper situation, and have a natural tendency to it--this element tending towards the highest parts, that towards the lowest, and another towards the middle.

This conjunction may for some time subsist, but not forever; for every element must return to its first situation.