Describe symbolism in Do Androids Dream of Electric Sheep? by Philip K. Dick

There are many symbols in this novel. The Donkey and the Toad are two symbols. They are both vanished species that mean a lot to Mercer: they symbolize humanity. Like the Toad, humans are highly adaptable. Humans even exist in outer space. Like the Donkey, humans are also beasts of burden who work until they die.