 This justification for clinical research faces several challenges. First, Rawlsian arguments typically are used to determine the basic structure of society, that is, to determine a fair arrangement of the basic institutions within the society (Rawls 1999). If the structure of society meets these basic conditions, members of the society cannot argue that the resulting distribution of benefits and burdens is unfair. Yet, even when the structure of society meets the conditions for fairness, it does not follow that individuals are obligated to participate in the society so structured. Competent adults can decide to leave a society that meets these conditions rather than enjoy its benefits (whether they have any better places to go is another question). The right of exit suggests that the fairness of the system does not generate an obligation to participate, but rather defends the system against those who would argue that it is unfair to some of the participants over others. At most, then, the present argument can show that it is not unfair to enroll a given individual in a research study, that this is a reasonable thing for all individuals, including those who are unable to consent.