Our pragmatist defense of democracy envisions active participation by citizens in processes of mutual discussion and persuasion. Such participation requires that each citizen be able to advance arguments that others might find persuasive. Thus, equal opportunity of political influence must attend to the conditions under which all citizens would be able to engage in discussion at this level. The depth of the anticipated participation highlights the importance of the effects of individual-level capacities for effective institutional performance. (p.234)In other words: One of the requirements for democratic institutions to work properly is that individuals must have the capacities (abilities) to participate effectively in deliberation. Presumably that means that most adults must be able to speak and/or write coherently enough to have the possibility of persuading others of their point of view.
Knight & Johnson proceed to criticize Rawls for paying "no explicit attention to issues of equality of capacity" (p.236). Citing Rawls's Political Liberalism [PL] (1993), they note Rawls's statement that everyone must have "a fair opportunity...to influence the outcome of political decisions" (PL, p.327). But, K&J continue, Rawls
limits analysis of [this] fair opportunity to the ownership of the minimum threshold of primary goods and merely assumes that actors possess the capacities needed to effectively use these resources.... On the dimension of moral and intellectual capacities and skills, Rawls concludes that any variations above the minimum threshold [of primary goods] are acceptable and consistent with the principles of justice as fairness. Ultimately, Rawls treats as an assumption what equality of capacity treats as a fundamental feature of political equality. (p.236; footnotes omitted)Perhaps Rawls would indeed be untroubled by some inequalities in capacities or, to put it differently, perhaps he doesn't focus explicitly enough on ensuring that individuals engaged in democratic deliberation have roughly equal capacities ("roughly" because obviously some inequality in capacities is unavoidable: not everyone has the eloquence of a Martin Luther King).
However, it's worth considering in this connection an implication of Rawls's views as expressed in A Theory of Justice [TJ]. There he says that "the primary social goods, to give them in broad categories, are rights and liberties, opportunities and powers, income and wealth," and -- importantly -- self-respect, i.e. "a sense of one's own worth" (TJ, 1971 ed., p.92). The sense of one's worth depends on a number of things, and one of them, Rawls suggests, is an ability to participate in the public life of one's society, as the following passage (p.101) indicates:
...the difference principle [i.e. the principle that social and economic inequalities must benefit the least advantaged] would allocate resources in education, say, so as to improve the long-term expectation of the least favored.... And...the value of education should not be assessed solely in terms of economic efficiency and social welfare. Equally if not more important is the role of education in enabling a person to enjoy the culture of his society and to take part in its affairs, and in this way to provide for each individual a secure sense of his [or her] own worth. (emphasis added)Thus, given the importance of self-respect in Rawls's view and the effects of the difference principle, the Rawlsian just society, at least as described in A Theory of Justice, would likely be one in which the large majority of adults would have the capacities needed to participate effectively in democratic deliberation and, more broadly, in their society's public affairs.