haersis

Haersis, also rendered hairesis, is a term derived from the Greek hairesis, from hairein meaning “to choose.” In its broad sense, haersis refers to a belief, doctrine, or school of thought that is chosen or adopted by a group. In classical usage the word could denote a particular philosophical opinion or system; in later Christian and European contexts it came to denote a doctrinal position deemed deviant from an established authority.

In early Christian literature, haeresis took on a more specific and often pejorative sense. It was used to label doctrines considered erroneous or divergent from what was regarded as apostolic tradition. Church fathers and theologians employed the term to distinguish orthodox belief from various dissenting opinions, and the concept played a central role in theological controversy, ecclesiastical discipline, and debates about doctrinal authority. The word entered Latin as haeresis and, through Latin and vernacular languages, developed into the modern terms for religious error.

Outside of its Christian polemical context, haeresis could be used more neutrally to indicate a philosophical or sectarian school of thought without immediate moral judgment. Over time, the term accumulated a predominantly negative connotation in many traditions, becoming the standard label for religious error or dissent.

Today, haersis or haeresis is discussed in studies of early Christian history, philosophy, and the history of ideas as a way to analyze how groups define boundaries of belief. The English-language equivalent is typically “heresy,” though the term retains nuance in its original Greek and in related European languages.