 Even though Parfit, despite his thorough investigations in Reason and Person, did not succeed in finding the sought-after ethical Theory X that would avoid the Repugnant Conclusion and other equally unattractive conclusions, this did not seem to destroy his hopes that such a theory could be found (Parfit 1984 p. 451). However, other theorists have regarded the search for this theory as having more gloomy prospects. This pessimism has been given a more formal content. It has been held that it can be proven that there is no population ethics that satisfies a set of apparently plausible adequacy conditions on such a theory. In fact, several such proofs have been suggested (Arrhenius 2000b, 2011). What such a theorem would show about ethics is not quite clear. Arrhenius has suggested that an impossibility theorem leaves us with three options: (1) to abandon some of the conditions on which the theorem is based; (2) to become moral sceptics; or (3) to try to explain away the significance of the proofs—alternatives which do not invite an easy choice (cf. Temkin 2012).