Rorty sees most cruelty as stemming from metaphysical questions like, "what is it to be human?", because questions such as these allow us to rationalize that some people are to be considered less than human, thus justifying cruelty to those people. In other words, we can only call someone "less than human" if we have a metaphysical "yardstick" with which to measure their prototypical human-ness. If we deprive ourselves of this yardstick (by depriving ourselves of metaphysics altogether), we have no means with which to dehumanize anyone.