19. But some one may, perhaps, say it is not proper to destroy that which belongs to the same tribe with ourselves; if the souls of animals are of the same essence with ourselves. If, however, it should be granted that souls are inserted in bodies voluntarily, it must be said that it is through a love of juvenility: for in the season of youth there is an enjoyment of all things. Why, therefore, do they not again enter into the nature of man? But if they enter voluntarily, and for the sake of juvenility, and pass through every species of animals, they will be much gratified by being destroyed. For thus their return to the human form will be more rapid. The bodies also which are eaten will not produce any pain in the souls of those bodies, in consequence of the souls being liberated from them; and they will love to be implanted in the nature of man. Hence, as much as they are pained on leaving the human form, so much will they rejoice when they leave other bodies. For thus they will more swiftly become man again, who predominates over all irrational animals, in the same manner as God does over men. There is, therefore, a sufficient cause for destroying other animals, viz. their acting unjustly in destroying men. But if the souls of men are immortal, but those of irrational animals mortal, men will not act unjustly by destroying irrational animals. And if the souls of brutes are immortal, we shall benefit them by liberating them from their bodies. For, by killing them, we shall cause them to return to the human nature. 20. If, however, we [only] defend ourselves [in putting animals to death], we do not act unjustly, but we take vengeance on those that injure us. Hence, if the souls of brutes are indeed immortal, we benefit them by destroying them. But if their souls are mortal, we do nothing impious in putting them to death. And if we defend ourselves against them, how is it possible that in so doing we should not act justly. For we destroy, indeed, a serpent and a scorpion, though they do not attack us, in order that some other person may not be injured by them; and in so doing we defend the human race in general. But shall we not act justly in putting those animals to death, which either attack men, or those that associate with men, or injure the fruits of the earth?