An apologia is a formal defense of an opinion, position or action. The term's current use, often in the context of religion, theology and philosophy, derives from Justin Martyr's First Apology and was later employed by John Henry Newman's Apologia Pro Vita Sua of 1864, which presented a formal defense of the history of his Christian life, leading to his acceptance by the Catholic Church in 1845. In modern usage, apologia describes a formal defense and should not be confused with the sense of the word 'apology' as an expression of regret; however, apology may mean apologia, depending on the context of use.