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 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. No animal, therefore, is eternal.
But your school, Balbus, allows fire only to be the sole active principle; an opinion which I believe you derive from Heraclitus, whom some men understand in one sense, some in another: but since he seems unwilling to be understood, we will pass him by. You Stoics, then, say that
