St. Vincent of Lerins

St. Vincent of Lérins was a monk of the famous island monastery of Lérins, off the southern coast of Gaul (modern France), in the fifth century, and died around 445. Little is known of the details of his life beyond that he had known the world before withdrawing to the peace of the monastery to devote himself to prayer and study, writing under the pen name 'Peregrinus' ('the Pilgrim').

His enduring legacy is his Commonitorium, in which he set out the classic test for distinguishing authentic Catholic teaching from novelty and heresy: that the faith to be held is what has been believed 'everywhere, always, and by all' (quod ubique, quod semper, quod ab omnibus) — the 'Vincentian Canon.' He also gave a celebrated account of the legitimate development of doctrine, likening the growth of the Church's understanding to the growth of a living body that remains ever itself. He is venerated as a saint and remains a touchstone for reflection on tradition and doctrine.