A Christian republic is a government that is both Christian and republican. As of the 21st century, the only countries in the world with a republican form of government and with Christianity as the established religion are Argentina, Costa Rica, Finland, Greece, Armenia, Samoa, Iceland, and Malta. Some other republics, such as Georgia, Peru, Guatemala, Panama, El Salvador, and Paraguay, give some credit or preference to Christianity, but without establishing it as the religion of the state. Others, such as Hungary, and Zambia, describe themselves as Christian countries. In A Letter Concerning Toleration, Locke wrote that "there is absolutely no such thing, under the Gospel, as a Christian Commonwealth". By this he meant that political authority cannot be validly founded upon Christianity. Rousseau, in On the Social Contract (in book 4, chapter 8), echoed this, saying that "I am mistaken in saying 'a Christian republic'; the two words are mutually exclusive.". However, Rousseau's point was subtly different, in that he was asserting that a civic identity cannot be moulded out of Christianity. David Walsh, founder of the National Institute on Media and the Family, acknowledges that there is a "genuine tension ... between Christianity and the political order" that Rousseau was acknowledging, arguing that "many Christians would, after all, agree with him that a 'Christian republic' is a contradiction in terms" and that the two live "in an uneasy relationship in actual states, and social cohesion has often been bought at the price of Christian universalism". Robert Neelly Bellah has observed that most of the great republican theorists of the Western world have shared Rousseau's concerns about the mutually exclusive nature of republicanism and Christianity, from Machiavelli (more on which later) to Alexis de Tocqueville. Rousseau's thesis is that the two are incompatible because they make different demands upon the virtuous man.