The word heresy comes from haeresis, a Latin transliteration of the Greek word meaning choosing, choice, course of action, or in an extended sense school of thought. Irenaeus (b. between the years 115 – 125 according to some, or 130 – 142, d. 202) defined heresy as deviation from the standard of sound doctrine.
Acts of the Apostles
The period 200 BC to 200 CE was a time of history-making changes in Jewish culture and religious and political philosophy. It also harbors the beginnings of the development of Christian philosophy, culture and beliefs. For these reasons events of that period still exerts considerable influence on large segments of Western philosophy and culture today. That is what makes it such an interesting period to study.