One of our great doctrines and also theological mysteries is that of the One, Holy and Undivided Trinity; the essence of the Father, the Son, and the Holy Spirit. It is a heady subject that has sparked debates and clashes over the centuries. But, how are we to know and understand something as seemly simple but also complex as the Trinity. Fr. John gives a brief outline of the Trinity's history as we understand it and also shows what the prime lesson we can learn from it is.