Schopenhauer used his pets to support his theory that selfhood is an illusion. Humans cannot help thinking of cats as separate individuals like themselves; but this is an error, he believed, since both are instances of a Platonic form, an archetype that recurs in many different instances. Ultimately each of these seeming individuals is an ephemeral embodiment of something more fundamental – the undying will to live, which, according to Schopenhauer, is the only thing that really exists.
