Philosophiae Doctor - PhD / A political arrangement is an arrangement for persons. Political arrangements are assessed in terms of the extent to which they manage the affairs of persons, which includes protecting their interests and entitlements. Political arrangements which are unable to protect the interests of its citizens, or a group of citizens, are deemed unacceptable, and where appropriate, alternative arrangements which do protect the interests and entitlements of its citizens are sought. In this thesis I argue that the political arrangement of John Rawls is unable to protect the interests and entitlements of the severely cognitively disabled who are regarded as full citizens by advanced political arrangements in the world today. I argue that it is the contract nature and conception of the person in Rawls’s system which excludes the severely cognitively disabled. This exclusion goes against our widely-held intuitions about the rights and entitlements of the severely cognitively disabled. I look to the Person Life View of Marya Schechtman, a conception of the person that includes the severely cognitively disabled, to see if a conception of the person that includes the severely cognitively disabled is able to solve the gap in Rawls’s system. I argue that it is not able to do so. I then propose a new way of approaching questions of personhood and appeal to the Aristotelian conception of the soul as the basis, arguing that membership of a type of organism typically considered a person is enough to be a complete member of that type and therefore a person.