When the Spirit of truth comes, he will guide you into all the truth; for he will not speak on his own, but will speak whatever he hears, and he will declare to you the things that are to come. He will glorify me, because he will take what is mine and declare it to you. (John 16:13-14)

Today is Trinity Sunday. Founded by Pope Pius X in 1911, it is the only feast day on the church calendar that does not celebrate a person or an event, but rather a doctrine, and some say, a reality. Trinity Sunday is celebrated the Sunday after Pentecost, and lasts only one day, which is symbolic of the unity of the Trinity.

It is a day that is given to celebrating and contemplating the Holy Trinity, one of the oldest and most widely accepted of all Christian beliefs and, if you don’t mind my saying so, one of…