One of the most delightful movies I have seen in a while was Shakespeare in Love, which won the Oscar for the best movie that year. One of the favorite lines throughout the movie was, "I don't know. It's a mystery."
And that's what I feel like saying every time Trinity Sunday comes around: "I don't know. It's a mystery."
Isn't that, in a way, what even Jesus is saying when he speaks of the wind or Spirit? The wind, like the Spirit, is a mystery. You cannot comprehend it or control it. The wind goes where it will (v. 8). So does the Spirit.