Augustine (354-430) is the most important Latin Church Father. His impressive oeuvre, which emerged at the intersection of antiquity and the Middle Ages, has uniquely shaped the philosophy and theology of the West. Augustine's theme is the philosophical interpretation of Christianity. His concepts of happiness, certainty, will, the political philosophy of the 'two kingdoms', psychological experience of time, the 'inner teacher', the Trinity, as well as grace and original sin are based on a philosophically mystical spirituality, where Neoplatonic and Christian traditional elements enter into an immediate connection.