Several years ago I heard a layperson preach, at an evangelical parish, on Trinity Sunday. I’ve got nothing against laypeople preaching, whether male or female. There’s a good chance they’ll be as qualified as the clergy and their homilies are liable to be no worse. The theme of his homily was hard to grasp, though, and seemed counter-intuitive, as he did little more than question the relevance of this feast day. Trinity Sunday, he said, is fairly recent, since it began in the medieval period. I suspect he was trying to make the perfectly valid point that, unlike other feast…