Maewyn Succat (pictured above), later to be known as St. Patrick, was a Christian converter, who used the shamrock as a metaphor for the holy trinity God, Jesus, and the Holy Ghost. I wonder what his excuse for four leaf clovers was then, God, Jesus, Holy Ghost and... Guinness.
St. Patrick's Cathedral in Dublin is actually quite beautiful. It reminds me nothing of St. Patrick's day, except the lawn is green. Put it on the list of things to see if you are ever in Ireland. I was going to attach a photo from my personal collection of Ireland photos, but facebook is not being cooperative.
So this St. Patty's day remember the reason for the season. God and Guinness.