This thesis focuses on what I call the question of exclusion. This question, I argue, is one that poses serious challenges to social contract approaches to justice and political legitimacy. In an intuitive way, the exclusion of some individuals seems to be a corollary of the social contractualist approach, which ascribes justice or legitimacy to a social arrangement insofar as it can be regarded as the product of the (actual – expressed or tacit – or hypothetical) consent of specified parties. (...) Consequently, this approach excludes those whose consent is not required in order to view an arrangement as legitimate or just. Given the enormous and continuing influence of John Rawls’s social contract theory, I take the Rawlsian view as my primary focus, concentrating on the way in which the question of exclusion raises challenges for Rawlsian contractualism. According to Rawls’s theory, those who participate in the hypothetical contract and to whom political power ought to be justifiable are reasonable and rational. They are reasonable in the sense that they understand and are willing to comply with the requirements of justice and they are rational in that they have the capacity to form, revise, and pursue a conception of the good. This gives rise to two categories of exclusion. In the first part of the thesis, I examine the exclusion of those who will develop the two moral powers sufficiently only if those who are represented in the social contract act (or refrain from acting) in certain ways. This category includes children, foetuses, and unreasonable citizens. Intuitively, justice issues in requirements in at least some of these cases, but it is hard to make sense of this on the Rawlsian approach. In the second part of the thesis, I address the question of exclusion regarding those who will never develop the two moral powers to the requisite degree, such as individuals with severe cognitive disabilities and non-human animals. Again, intuitively, justice issues in requirements here, but their justification is not clear on the contractualist approach. My conclusion is threefold. First, I argue that the problems the question of exclusion poses cannot be addressed by a single solution. Second, I safeguard Rawlsian contractualism by showing how each problem can be resolved. Third, I offer policy-prescriptions on a number of issues, such as education, abortion, and the criminal justice system. (shrink)