Abstract: Do motivational limitations due to human nature constrain the demands of justice? Among those who say no, David Estlund offers perhaps the most compelling argument. Taking Estlund’s analysis of ‘ability’ as a starting point, I show that motivational deficiencies can constrain the demands of justice under at least one common circumstance – that the motivationally deficient agent makes a good faith effort to overcome her deficiency. In fact, my argument implies something stronger; namely, that the demands of justice are constrained by what people are sufficiently likely to be motivated to do. Thus, contrary to the prevailing wisdom, it is the business of ideal theory – not just nonideal theory – to work with the motivational capacities people are likely enough to have.