There appears to be a tension between two commitments in liberalism.
The first is that citizens, as rational agents possessing dignity, are owed a
justification for principles of justice. The second is that members of society who
do not meet the requirements of rational agency are owed justice. These notions
conflict because the first commitment is often expressed through the device of the
social contract, which seems to confine the scope of justice to rational agents. So,
contractarianism seems to ignore the justice claims of the severely cognitively
impaired. To solve this problem, Martha Nussbaum proposes the capabilities
approach. The justifiability condition, on this approach, is met by the idea of
overlapping consensus. This essay argues that overlapping consensus cannot meet
liberalism’s justifiability condition, nor is it more inclusive of the cognitively
impaired. Therefore, we have reason to retain the contract device and look for
another way to ensure that liberalism respects the justice claims of all.