From an address the Pope gave last March in St. Peter's Square on St. Irenaeus, whom he called the "first theologian:"
There is a beautiful expression that Irenaeus uses in the book "Against Heresies": "The Church, having received this preaching and this faith, although scattered throughout the whole world, yet, as if occupying but one house, carefully preserves it. She also believes these points (of doctrine) just as if she had but one soul, and one and the same heart, and she proclaims them, and teaches them, and hands them down, with perfect harmony, as if she possessed only one mouth. For, although the languages of the world are dissimilar, yet the import of the tradition is one and the same. For the Churches which have been planted in Germany do not believe or hand down anything different, nor do those in Spain, nor those in Gaul, nor those in the East, nor those in Egypt, nor those in Libya, nor those which have been established in the central regions of the world."We can already see at this time -- we are in the year 200 -- the universality of the Church, its catholicity and the unifying force of truth, which unites these so-very-different realities, from Germany, to Spain, to Italy, to Egypt, to Libya, in the common truth revealed to us by Christ.
This is, to use the word so beloved of the multiculturalists, diversity, in the happiest sense: people of wildly disparate backgrounds but because they are united in and by One, Holy, Catholic and Apostolic Church are able to preserve and celebrate their differences. To insist there can be pluralism in faith, as the lefty cultural relativists do, can only lead to balkanization, chaos and, well, Protestantism.
(Thanks to Diogenes)