Saint Gildas (c. 494 or 516-c. 570) was a prominent member of the Celtic Christian church in Britain, whose renowned learning and literary style earned him the designation Gildas Sapiens (Gildas the Wise). He was ordained in the Church, and in his works favoured the monastic ideal. Fragments of letters he wrote reveal that he composed a Rule for monastic life that was a little less austere than the Rule written by his contemporary, Saint David, and set suitable penances for its breach. One of his most important works is De Excidio Britanniae or On the Ruin of Britain. The book is a sermon condemning the acts of his contemporaries, both secular and religious.