[Each Thursday, we “reflect” on a hymn suggested by our readers. If you would like to add your favorites to our list, leave a comment with no more than 3 suggestions.] Outside of the songs that come directly from the pages of Scripture, “Be Thou My Vision” is one of the oldest songs still in regular use among Christians. The words come from an old Irish hymn, and are estimated to be from the 8th Century. This history suggests why you will often hear the tune played in Celtic instrumentation, and will sometimes still hear it in movies and TV shows. “Be Thou My Vision” is a song of deep…