“One cannot breathe as Christians, I would say more, as Catholics, with only one lung; one must have two lungs, that is, the Eastern and the Western lungs.” Thus the words of St. John Paul II in his address to representatives of non-Catholic Christian communities on May 31st, 1980, recalling his visit to the Ecumenical Patriarchate of Constantinople. This invitation of St. John Paul II resonates with even greater force today, in a world that is increasingly globalized but – at the same time – torn by conflicts and tensions. This course aims to rediscover and deepen that Christian spirituality – both Eastern and Western – that enable us to “breathe” with “both lungs.” During the course, various theological methods will be applied to the sources of Revelation: the Holy Scriptures, Tradition, and especially the spiritual and cultural legacy of the Church Fathers and of the Saints. The inductive-deductive method will lead to the systematic one; on the other hand, in the more specific analysis of some theological texts, the phenomenological and hermeneutical approach will be essential for a correct understanding and interpretation of the sources, especially considered from the standpoint of Spiritual Theology.