An apologia (Latin for apology, from Ancient Greek: ἀπολογία, lit. 'speaking in defense') 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 (AD 155–157) and was later employed by John Henry Newman's Apologia Pro Vita Sua (English: A Defense of One's Own Life) 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 Ancient Greece, an apologia was primarily used as a legal defense: The accuser would present a kategoria, or accusation, and the defendant would present his apologia, or defense. In modern usage, apologia describes a formal defense of an idea or belief, rather than against a legal charge. In both ancient and modern uses it different from an apology, or expression of regret. The main difference between the two is that the act of apologizing is meant to express regret, and the purpose of an apologia is to clearly communicate the rational grounds for a belief or position. As an example, a person might apologize for bumping into another person, but could write an apologia to explain why they believe a specific belief is superior to another specific belief. Source: Wikipedia (en)