Faith in action: John Paul II’s social mastership in his pronouncements to Brazil. This doctorate thesis in Systematic-Pastoral Theology consists in a study about the social thought of the Catholic Church. The physical object here analyzed is the conjunct of words uttered by the Pope John Paul II on the occasion of his three pastoral visits to the Brazilian territory, and on the occasion of four ad limina apostolorum visits of the Bishops of Brazil to Rome. The thesis in its whole clears up about the reasons of the Christian action in the world, about the religious and ethical directives of that action, about the danger of the ideologies to take on the place of Theology, and about the principles that serve to direct believers and non-believers’ way of to act. The axis and the dimension around which establishes John Paul II’s social mastership systematization to Brazil are the Christological and anthropological axis, and the social-transformer dimension. In the Christological axis stands out the scatological dimension of the understanding and of the aims of the Christian action in the world. In the anthropologic axis stand out, starting from a Christian Anthropology, the ethical basic principles of the Christian action in the worldly order. In the socialtransformer dimension stand out, by the light of scatology and of the Christian ethics, the directives of the specific compromise of every person called to the social life.