Friends, here is the curious thing about the Trinity: at one and the same time, it is the most extraordinary and the most ordinary of Christian doctrines, simultaneously the most inaccessible and the most obvious.
On the one hand, there is a highly developed, technical language regarding this great mystery. On the other hand, the most ordinary Catholic simply and regularly invokes the Trinity every time he crosses himself.
Our Gospel for Trinity Sunday is taken from the very end of Matthew’s Gospel. The risen and glorified Lord speaks to the new Israel of the Church, “All power in heaven and on earth has been given to me.” This is not an ordinary prophet speaking. This is the very Word of the Father, the very imprint of the Father’s being.
Jesus then tells them to go forth and to do the work of gathering in, of drawing people into the very dynamics of the divine life. Now, how all of this fits together theoretically is indeed a fascinating question, but we should never allow the arcane language of theology to obscure the revolutionary meaning of the Trinity: it is a summons to mission, a call to action.