ications of the principle of fair play. 1 Why Follow the Rules? Zhu's argument for the justificatory gap relies on an appeal to intuition: it seems that there are many forms of reciprocation that could provide a fair return for benefits produced by the cooperative efforts of others. So long as the return is fair, Zhu says, it does not matter what form it takes. The burden of the fair play theorist is to explain why some loose form of reciprocation is not a sufficiently fair return, and that cooperation-submission to the rules-is. Put in terms of rights, the issue is whether incurring a duty of fair play involves forfeiting a liberty right to choose how one repays one's debt of fairness. The standard argument from fair play theorists is that giving up the liberty right to repay as one chooses is part of the cost paid by the scheme's other participants, and so those with outstanding debts of fairness must take on that cost, too. This alone cannot settle the issue, of course, because Zhu could simply reply that an alternative fair repayment would take into account-and provide compensation for-the extra benefit of choosing the form of repayment. So there will have to be some further reason to cooperate rather than reciprocate if the justificatory gap is to be avoided. Zhu considers one possible reply on behalf of requiring cooperation: if everyone were free to choose the form of their reciprocation, then any cooperative 3Playing Fair and Following | doi 10.1163/17455243-46810054 journal of moral philosophy (2016) 1-8 <UN> scheme would inevitably collapse. Freely chosen reciprocation would, then, fail to restore the just distribution of benefits and burdens. Thus, fair play requires cooperation, rather than freely chosen reciprocation.3 Call this the actual consequences argument. As I read Zhu, he offers two replies to this argument. First is that the actual consequences argument cannot ground a requirement of cooperation, because cooperative schemes generally do not depend on support from those bound only by a duty o