 Simon Blackburn derived quasi-realism from a Humean account of the origin of our moral opinions, adapting Hume's genealogical account in the light of evolutionary game theory.To support his case, Blackburn has issued a challenge, "Blackburn's Challenge", to anyone who can explain how two situations can demand different ethical responses without referring to a difference in the situations themselves.Because this challenge is effectively unmeetable, Blackburn argues that there must be a realist component in our notions of ethics.