  A further worry is that it is not clear that having the belief best increases reproductive fitness.  De Lazari-Radek and Singer argue, in reply to the objection that their argument takes away the justification for believing that pain is bad, that there is no advantage to believing that pain is bad; I am sufficiently motivated to avoid pain without any such belief (de Lazari-Radek and Singer 2014 268–269; for the general point, see Parfit 2011 v. 2 527–30).  The same seems to go for rational egoism: I am sufficiently motivated to act egoistically without any belief in the truth of rational egoism.