And it is thought that every animal has its own special pleasure, just as it has its own special function: namely, the pleasure of exercising that function. This will also appear if we consider the different animals one by one: the horse, the dog, man, have different pleasures—as Heracleitus says, an ass would prefer chaff to gold, since to asses food gives more pleasure than gold. Different species therefore have different kinds of pleasures. On the other hand it might be supposed that there is no variety among the pleasures of the same species.