A second normative consideration stems from the importance given to personal responsibility in contemporary political philosophy. If one believes that one should strive for equality of capability, then each person should have the same real opportunity (capability), but once that is in place, each individual should be held responsible for his or her own choices. This responsibility-sensitivity principle is widely endorsed not only in political philosophy but also in the mathematical models being developed in normative welfare economics. If one wants to endorse and implement this principle of responsibility-sensitivity, then specifications and applications of the capability approach should focus on capabilities, rather than functionings. Yet even at a highly abstract theoretical level, philosophers disagree on whether we should endorse responsibility-sensitivity in developing the capability approach (e.g., Fleurbaey 2002; Vallentyne 2005; Wolff and de-Shalit 2007). Moreover, for applied work, serious epistemological hurdles may ultimately lead us to drop the responsibility-sensitive principle for practical reasoning about the actual world.