The Orthodox Church defines heresy as " a strange doctrine". Dictionary.com defines it as 1. opinion or doctrine at variance with the orthodox or accepted doctrine, esp. of a church or religious system. 2. the maintaining of such an opinion or doctrine. 3. In the Roman Catholic Church . the willful and persistent rejection of any article of faith by a baptized member of the church. 4. any belief or theory that is strongly at variance with established beliefs, customs, etc. Today heresy can be euphemistically called a "dangerous idea". The patron saint of heretics could be Galileo Galilei. The famous "heresy" quote from this first modern scientist is It is surely harmful to souls to make it a heresy to believe what is proved [By Science]. Galileo's thesis throws a spanner [or for American English users "monkey wrench] to the maintainers of orthodoxy. Orthodoxy may not represent truth at all and thus the orthodoxy may really endanger souls. A
"It is surely harmful to souls to make it a heresy to believe what is proved" - Galileo