What term refers to an opinion or doctrine that goes against established religious beliefs, especially those of Christianity?

The term that refers to an opinion or doctrine that contradicts established religious beliefs, particularly those of Christianity, is heresy. In religious contexts, heresy specifically denotes beliefs that diverge from the core doctrines, authority, or teachings of a faith. Heresy poses a challenge to the orthodoxy of the religion, leading to potential theological disputes and conflicts within the community.

In Christianity, for example, heretical beliefs can often lead to significant consequences, including excommunication or persecution, as they threaten the unity and purity of the faith. This concept is historically significant as it has shaped the development of religious institutions and their responses to various theological interpretations throughout history.

The other terms do not capture this specific meaning. Idolatry refers to the worship of idols, which, while regarded as contrary to Christian doctrine, is not synonymous with holding differing views or interpretations. Illustrious refers to something that is well-known or distinguished, and illicit pertains to something that is illegal or forbidden, neither of which relates directly to the religious context of diverging beliefs.