This site is adding a section in the table of contents on heresies.
There are several definitions for the word heresy. The one that many are familiar with is that heresy is a belief that rejects the orthodox tenets of a religion.  That sounds simple enough, but it is actually more complicated than that. Heresy comes from the Greek word “hairesis” which means to divide. With that, we see that heresy really refers to any doctrine that causes a group to split. The negative connotation is that the doctrine that is labeled the “heresy” is the erroneous one because it caused a division within a group which in religious groups is not desirable. With that in mind, it is easy to see that both sides of a group that split over an issue will call the other side heretics. The Pope called Martin Luther heretic while Martin Luther rejected papal doctrine on indulgences and other issues as heresies because they were erroneous and egregious enough for Luther to split from the Catholic Church.
“In Christian usage, the term “heresy” refers to a false doctrine, i.e. one which is simply not true and that is, in addition, so important to those who believe it, whom the Church calls heretics must be considered to have abandoned the faith.”
In original, primitive Christianity heretics were more easily seen to be “outside” the faith. In modern times the distinction gets blurred. With tens of thousands of churches and denominations in various degrees of dispute, what is the legitimate line of demarcation between a serious doctrinal dispute and petty issues? Some have isolated heresies to what they proclaim as a few supremely important doctrines, such as the deity of Christ and the Trinity, and made those the only critical doctrines that all Christians must agree on. While that is an understandable attempt, it falls short in reality because there are many issues, many of which are enumerated on this website, which cause divisions so bitter and/or so severe that believers from the different sides do not fellowship with each other, and in fact, may become bitter enemies. In my time I have seen Baptists decree Pentecostals as “of the devil.” History shows that people were banned, tortured, and even killed for issues like “believers baptism”, the belief that to be baptized one must be of the age of reason, and choose to be baptized, probably by immersion in water.
I have chosen to make this section on heresies because a lot of them will be mentioned in the section on movements and other places. Beginning with the apologists in early Christianity, writers throughout history have been addressing heresies.
Intricately involved with the idea of heresy is the concept of orthodoxy. Orthodoxy means right doctrine. And of course, right doctrine depends on which side of the argument you’re on. So once we get to, let’s say, the Reformation we will begin to see that Lutheran orthodoxy is different from Catholic orthodoxy.
There have been many heresies proclaimed throughout the ages including Docetism, Gnosticism, Marcionism, Montanism, adoptionism, modalism, and Arianism. Issues like freedom of will, mode of baptism, church government, justification by grace, state-run churches, participation in war, down to modern issues like abortion, gay marriage and ordination, women’s ordination, and church involvement in social issues have all resulted in charges of heresy on one side against another.
As always, the focus of these articles will be to compare whatever stand is taken against the standards of original, primitive Christianity.
 HERESIES, Heresy And Orthodoxy In The History Of The Church, Harold O. J. Brown, Hendrickson Publishers, Peabody, Mass 2000, p. 1
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