Pius XI issued numerous encyclicals, including Quadragesimo anno on the 40th anniversary of Pope Leo XIII's groundbreaking social encyclical Rerum novarum, highlighting the capitalistic greed of international finance, the dangers of socialism/communism, and social justice issues, and Quas primas, establishing the feast of Christ the King in response to anti-clericalism. The encyclical Studiorum ducem, promulgated 29 June 1923, was written on the occasion of the 6th centenary of the canonization of Thomas Aquinas, whose thought is acclaimed as central to Catholic philosophy and theology. The encyclical also singles out the Pontifical University of Saint Thomas Aquinas, Angelicum as the preeminent institution for the teaching of Aquinas: "ante omnia Pontificium Collegium Angelicum, ubi Thomam tamquam domi suae habitare dixeris" (before all others the Pontifical Angelicum College, where Thomas can be said to dwell). The encyclical Casti connubii promulgated on 31 December 1930 prohibited Catholics from using contraception.
Pius XI issued numerous encyclicals, including Quadragesimo anno on the 40th anniversary of Pope Leo XIII's groundbreaking social encyclical Rerum novarum, highlighting the capitalistic greed of international finance, the dangers of socialism/communism, and social justice issues, and Quas primas, establishing the feast of Christ the King in response to anti-clericalism. The encyclical Studiorum ducem, promulgated 29 June 1923, was written on the occasion of the 6th centenary of the canonization of Thomas Aquinas, whose thought is acclaimed as central to Catholic philosophy and theology. The encyclical also singles out the Pontifical University of Saint Thomas Aquinas, Angelicum as the preeminent institution for the teaching of Aquina.s: "ante omnia Pontificium Collegium Angelicum, ubi Thomam tamquam domi suae habitare dixeris" (before all others the Pontifical Angelicum College, where Thomas can be said to dwell). The encyclical Casti connubii promulgated on 31 December 1930 prohibited Catholics from using contraception