Ask a Catholic priest which Sunday is the most daunting one to preach on, then there’s a good chance he’ll say Trinity Sunday. There are two obvious dangers when it comes to preaching on Trinity Sunday. The first is for the preacher to deliver a perfectly orthodox sermon, but one that uses so much abstruse theological terminology that only a trained theologian could hope to follow it. The second danger is that the preacher tries too hard to deliver a simple and engaging sermon, and in the process inadvertently commits some major heresy.