The option for the poor or the preferential option for the poor is the fourth of the key themes of Catholic social teaching. The phrase option for the poor was used by Father Pedro Arrupe, S.J. in 1968 in a letter to the Jesuits of Latin America. As a developed theological principle it was first articulated by Fr. Gustavo Gutierrez, O.P. in his landmark theological book, A Theology of Liberation, the principle is rooted in both the Old and New Testaments and claims that a preferential concern for the physical and spiritual welfare of the poor is an essential element of the Gospel. This principle was articulated by the Catholic Bishops of Latin America as well as by several popes, particularly Pope John Paul II.