Liberation theology is a Christian theological approach emphasizing the liberation of the oppressed. In certain contexts, it engages socio-economic analyses, with "social concern for the poor and political liberation for oppressed peoples". In other contexts, it addresses other forms of inequality, such as race or caste. Liberation theology is best known in the Latin American context, especially within Catholicism in the 1960s after the Second Vatican Council, where it became the political praxis of theologians such as Frei Betto, Gustavo Gutiérrez, Leonardo Boff, and Jesuits Juan Luis Segundo and Jon Sobrino, who popularized the phrase "preferential option for the poor". This expression was used first by Jesuit Fr. General Pedro Arrupe in 1968 and soon after the World Synod of Catholic Bishops in 1971 chose as its theme "Justice in the World". The Latin American context also produced Protestant advocates of liberation theology, such as Rubem Alves, José Míguez Bonino, and C. René Padilla, who in the 1970s called for integral mission, emphasizing evangelism and social responsibility. Theologies of liberation have also developed in other parts of the world such as black theology in the United States and South Africa, Palestinian liberation theology, Dalit theology in India, and Minjung theology in South Korea. Latin American liberation theology The best-known form of liberation theology is that which developed within the Catholic Church in Latin America in the 1960s, arising principally as a moral reaction to the poverty and social injustice in the region, which Cepal, deemed the most unequal in the world. The term was coined in 1971 by the Peruvian priest Gustavo Gutiérrez, who wrote one of the movement's defining books, A Theology of Liberation. Other noted exponents include Leonardo Boff of Brazil, and Jesuits Jon Sobrino of El Salvador and Juan Luis Segundo of Uruguay. Latin American liberation theology influenced parts of the evangelical movement and Catholic bishops in the United States. Its purported use of "Marxist concepts" led in the mid-1980s to an admonition by the Vatican's Congregation for the Doctrine of the Faith (CDF). While stating that "in itself, the expression 'theology of liberation' is a thoroughly valid term", the prefect Cardinal Ratzinger rejected certain forms of Latin American liberation theology for focusing on institutionalized or systemic sin and for identifying Catholic Church hierarchy in South America as members of the same privileged class that had long been oppressing indigenous populations from the arrival of Pizarro onward.