 Some kinds of cognitive success involve compliance with a constraint, while others involve the realization or promotion of values. We can contrast these two kinds of success by contrasting the associated kinds of failure: failure to comply with a constraint results in impermissibility, whereas failure to realize some values results in  sub-optimality.[8]  Of course, if sub-optimality is always impermissible and vice versa, then the extension of these two categories ends up being the same, even if the two categories are not themselves the same. But it is implausible to regard all sub-optimality as epistemically impermissible: cognitive success does not require us to be perfectly cognitively optimal in every way. If cognitive success is ever achievable even in principle, then at least some degree of cognitive sub-optimality must be permissible. Achieving greater optimality than what’s required for cognitive permissibility could then be understood as cognitive supererogation. If such supererogation is possible, at least in principle, then the permissible can fall short of the optimal.