Before looking at the question of lexical ranking, however, it is as well to remember the basis of non-ideal theory. If ideal theory is defined by Rawls as concerned with conditions of strict compliance then, naturally enough, non-ideal theory looks at non-compliance in certain respects but there are two kinds of non-compliance defined. One concerns "natural limitations and historical contingencies", the other how to "meet" injustice. Our duty is to remove, as far as possible, conditions of injustice but this is where intuition has a role. The lexical ordering of principles defines a way in which such intuitive judgment is guided. When this is done a further methodological device is invoked by Rawls in section 39 of Theory: that of the "representative equal citizen" (or, as he was once termed in British jurisprudence, "the man on the Clapham omnibus"). The reason for invocation of the notion of this representative is to apply the idea of the "common interest" where the common interest is a means of describing conditions that are to the advantage of all.
When this notion is applied to Rawls' general principles of justice some interesting results emerge with regard to how non-ideal theory is envisaged. So, for example, if we connect these notions to the general principle of liberty, then, states Rawls, there are ways that this principle can be legitimately restricted. So freedom of thought has to be exercised in a sense that is consistent with public order and this relationship is one that is part of what Rawls terms "the permanent conditions of human life" so this balance is one that is part of the area of non-ideal theory that concerns natural limitations. By contrast, if we look at other restrictions on liberty we can see how those connect with the other element of non-ideal theory. One way the principle of liberty gets restricted concerns the degree of tolerance given to those who lack tolerance themselves. This is part not of adjustment to natural limitations but instead to the principles for "meeting" injustice, or, as Rawls also describes this part, to the "partial compliance" part of non-ideal theory.
After outlining the relationship of non-ideal theory to the principle of liberty Rawls next turns to how it relates to the principle of equality. The restriction of application of the principle of equality occurs when unequal situations are allowed to arise and governed by some kind of rule. In some situations, for example, as envisaged in part by Kant in the Doctrine of Right, a division is allowed between active and passive citizens with the former having a larger role granted to them in public life than the latter. This inequality is not one that leads to systematic devaluation of those in the passive class since, as in Kant's own case, it can be fitted with a general argument against serfdom and slavery. Since the latter are ruled out on some appeal to the basic condition of liberty there is some sense in which this basic condition can be defended even though the application of it in principle permits unequal standing of citizens. So, in some sense, Kant gave priority to liberty over equality in relation to the standing of citizens (as well as in other respects) and Rawls agrees with this asserting the lexical priority of liberty over equality.
Rawls' own two principles are stated in section 11 of Theory and are worth citing:
First: each person is to have an equal right to the most extensive scheme of equal basic liberties compatible with a similar scheme of liberties for others. Second: social and economic inequalities are to be arranged so that they are both (a) reasonably expected to be to everyone's advantage, and (b) attached to positions and offices open to all.When they are laid out it is evident that, whilst the principle of the lexical priority of liberty is similar in Theory to the one provided in the Doctrine of Right that the application of it is different. The second part of Rawls' second principle makes clear that the inequality permitted is not one of distinction between active and passive citizens since there should be a basis for anyone being able to hold any position. (It would be worth, on a different occasion, looking at the problems Kant would have with a similar declaration despite being often close to it.)
The second part of the second principle is often described as an "equal opportunity" principle whilst the first part is the Difference Principle. The second principle is lexically derivative of the first principle but, whilst both can be restricted, the ground of the restriction must be one that can be generally justified to and for those who are disadvantaged by its application. The point of including the discussion of the lexical priority of the principles is made clearer by Rawls in his late piece Justice as Fairness: A Restatement. In this late work Rawls suggests that the idea of the well-ordered society described in ideal theory should be able to provide guidelines for non-ideal theory including the problem of how to "deal with" ( or "meet" as he put in Theory) injustice. This requires, as we have uncovered, indicating the way in which injustice arises "naturally" in some sense as opposed to how it is part of real non-compliance. But this further needs to be understood by means of the lexical priority of the principles of justice since otherwise the degree of the real non-compliance would be entirely left to intuition. With the lexical priority added this intuitive element begins to be governed by a specific type of rule. In some subsequent postings I'll begin to probe the implications of these conceptions for how non-ideal theory gets laid out by Rawls.