The diagram further makes clear that the theory of right covers not only the "basic structure" and individuals but also the "law of nations", the latter being finally described by Rawls in The Law of Peoples, some years after the publication of Theory and in a fashion that many Rawlsians (particularly Pogge) were puzzled by. Leaving the discussion of the "law of nations" aside, however, Rawls' diagram makes of the reference to individuals two forms of discussion, firstly in relation to requirements on individuals and secondly permissions given to them. The account of requirements is further sub-divided between obligations and natural duties. Obligations of individuals are circumscribed in terms of fairness and fidelity whilst natural duties are either positive or negative. Positive natural duties involve upholding justice, providing mutual aid and mutual respect. Negative natural duties are restricted to prohibitions on injury and particularly on harm to "innocents". Finally, the theory of permissions is restricted to ones which are either indifferent (of which Rawls says nothing) or supererogatory (involving beneficence, courage and mercy). All this indicates at the very least that the theory of social justice was conceived at the time of writing Theory as only a small part of the general theory of right that Rawls imagined.
However despite the indication the diagram provides of an expansive general theory of right Rawls provides little within the pages of Theory to address its outline. The two sections under review are the major attempt made in the work to look at such a general theory and have been, as indicated above, little addressed in the literature on the work. (They are, however, supplemented by the first two sections of Chapter VI where the two principles for individuals are given further treatment.) One of the reasons why this is likely to be so, apart from the brevity of Rawls' discussion of these principles for individuals is that he also makes clear that in the original position he believes that the principles for individuals would be selected after the principles definitive of the "basic structure". This point is motivated by the argument that principles for individuals presuppose some form of social structure already in place though this is far from obvious to anyone who has studied the history of moral and political philosophy. In support of this Rawls refers, somewhat unexpectedly, to Francis Herbert Bradley, one of the pre-eminent British Idealists, who argued that "the individual is a bare abstraction" something taken by Rawls to mean that obligations and duties presuppose a moral conception of institutions. This interpretation of Bradley's statement is deflationary of it but the key point is that moral conceptions of institutions might be taken by some to arise from principles of individuals (if you were committed to "methodological individualism"). That Rawls takes it to be obvious this is not so is a comment on his understanding of method in political reasoning.
The result of the reference to the "original position" is that the principles of right are understood in general by Rawls to be principles that are in accord with what would be chosen in the original position. This is something that Rawls correctly understands as a revisionary approach to the concept of right so that "rightness as fairness" is intended to replace the general views of right held otherwise though it does so without reference to work on value or moral worth, something that might well surprise both Kantians and others working in moral theory.
Having made these general points it is time to consider the actual principles for individuals that Rawls provides. The first such is a principle of fairness as one would expect given that we are dealing with a view of "rightness as fairness". This notion of fairness is meant to cover the requirements on individuals that are treated as obligations rather than as natural duties. "This principle holds that a person is required to do his part as defined by the rules of an institution when two conditions are met: first, the institution is just (or fair), that is, it satisfies the principles of justice; and second, one has voluntarily accepted the benefits of the arrangement or taken advantage of the opportunities it offers to further one's interests."
Stated in this general form the principle of fairness specifies obligations in relation to institutions and so this principle for individuals is part of Rawls' general account of institutions. Given that we have already described the two principles of justice as the means by which institutions should be governed the first part of the principle of fairness simply enjoins that individuals should conform to the institutions that are socially just. It is the second element that adds something that is specific to individuals in the form of reference to voluntary engagement in the institution including acceptance of its advantages. This principle is clearly meant to ensure that mutual benefit really arises from the institutions in question and to prevent encouragement of "free riders". Hence Rawls takes the two principles of justice as defining what is "a fair share" between us given that we adhere to the principle of fairness.
One of the consequences that follows from Rawls' treatment is that one is under no obligation with regard to institutions that are patently unjust, something that would appear to rule out the kind of problem Kant is thought to run into when faced with questions about the right of rebellion. However this point clearly belongs to non-ideal theory where it would require some nuance since there are different kinds of unjust institution and some might be thought to be worth some form of fidelity even given the injustice they are incarnations of. (This is the rationale in a sense for adopting what Kant, in Perpetual Peace, refers to as "preliminary" principles.)
Obligations are generally understood by Rawls as produced by institutions which "specify what it is that one is required to do". However given that institutions include such things as promises this is not in itself sufficient to show that the principle of fairness has to be defined only in terms of the first part of the principle in relation to pre-defined general principles of social justice since the notion of a promise has a standing separate from any given particular nature of "basic structure".
Whilst Rawls describes obligations in general by reference to the principle of fairness he has no corresponding overall principle for addressing natural duties. If natural duties include duties of mutual aid and non-maleficence then it would appear that these duties would belong more naturally to a theory of virtue than to a theory of right since it is far from clear how there can be strict enforcement of such duties. Inclusion of them as part of a theory of virtue would, however, require Rawls to revisit the diagram provided and give more room to the general discussion of practical reason rather than leaving everything to be determined as part of right and this he shows no inclination to do.
Rawls distinguishes between positive and negative natural duties and assumes that negative ones have priority over positive ones although he simply makes this remark and does nothing to provide a justification of it. Natural duties are distinct from obligations in that they apply without regard to voluntary acts. The duty, for example, not to be cruel, does not require that I first have voluntarily joined something or am part of some institution that defines the sense of cruelty. So promises are not required as part of the theory of natural duties. Natural duties are also general in form, holding between all moral persons. Interestingly, one of the reasons for holding natural duties to be part of the theory of right is that Rawls takes it that such natural duties are also part of the theory of war.
The key natural duty for Rawls, however, is the duty to be just. This evidently echoes the first part of the principle of fairness. Under this understanding we all have a natural duty to act in such a way that just conduct is encouraged. Since natural duties are not, however, derived from contractual promises, the general duty to uphold fairness is not a part of Rawls' contractarianism but is rather a moral reason to support the outcome of the original position. There thus can be two kinds of reason that support a particular form of action, one that is "natural" and one that is social. Since principles of natural duties are also general they apply to all in a way that the principle of fairness does not since the latter really applies to those holding positions within institutions.
This leaves the understanding of permissions that Rawls' diagram referred to and which he states little about. Permissions are acts we are at liberty to perform as they do not violate obligations or natural duties. Since they do include the territory of supererogatory actions it remains true that a theory of permissions is not without substantive interest in moral theory. Rawls, however, says virtually nothing about this except to mention that it appears utilitarianism cannot recognise this category since it appears to require from all actions that most would take to be supererogatory.