Heresy is any provocative belief or theory that is strongly at variance with established beliefs or customs. A heretic is a proponent of such claims or beliefs. Heresy is distinct from both apostasy, which is the explicit renunciation of one's religion, principles or cause, and blasphemy, which is irreverence toward religion.The term is usually used to refer to violations of important religious teachings, but is used also of views strongly opposed to any generally accepted ideas.