By the end of the fourth century, the doctrine of the Trinity as it is known today has largely been developed through the efforts of the Pro-Nicene Fathers. This article discusses the major theological achievements of the Cappadocian father, Basil of Caesarea, focusing on his elucidation of the conceptual and terminological differences between the terms ousia and hypostasis which allows for the distinctiveness of the three Persons within the unity of the Godhead. In addition, his understanding of the concept of epinoia is highlighted as a means of derivation of the knowledge of God that avoids both hyper-rationalism and agnosticism