Leo Pfeffer summed up many people's views on religious categories when he said, "If you believe in it, it is a religion. If you do not care about it, it is a sect. If you fear and hate it, it is a cult."This may be how most people categorize religious groups but it is, of course, both inaccurate and unfair. Dictionaries are little help as they often muddle distinct categories due to muddled usage of terms. Nor does etymology serve to solve the problem (e.g. "cult" simply meant "religion" although almost no one uses it that way anymore).

What I offer here are my own personal definitions. They seem to fit popular usage and also serve to highlight distinctives.

Religion: a group centered around one or more ultimate beliefs about life. They usually include a given set of essential doctrines as well as secondary dogmas.   Sect: a group that accepts all of the essential doctrines of the parent religion, but deviates seriously from secondary dogmas by adding to or subtracting from traditional teachings.   Denomination: a group within a religion / sect that accepts all of the essential doctrines of the parent religion, but disagrees on accepted secondary dogmas (usually within traditional boundaries).   Cult: a group that denies one or more essential doctrines of its parent religion, and any number of secondary dogmas. Social characteristics of a cult include authoritarian control over beliefs and lives, intolerance of the members of other belief systems, isolationism, etc.

So for example, a Presbyterian is a denomination of Protestantism which is a sect of Christianity. Mormonism is a Christian cult while Buddhism is a completely different religion.

Following this scheme many popular "cults" are really just heretical "sects" (denominations might be considered orthodox sects).  A cult, if it survives long enough, it might become considered as a sect, which, if it continues to grow, could become a religion (E.g. Christianity might be seen as a sect of Judaism). Now, many sects do indeed share many of the typical characteristics of a sociological cult such as authoritarian control over beliefs and lives, intolerance of the members (as opposed to the teachings) of other belief systems, a divisive "us vs. them" mentality, etc. So a theological sect can also be a sociological cult. Yes, it's all very confusing and that is why we must be careful with our terms.

Terminology

Speaking of terms, here are some others that are often confused - even in the dictionary. These terms are very fluid so we should not be dogmatic (in fact "dogmatic" is one of the terms!) about the definitions, but these seem to fit general as well as academic usage:

• Doctrine: Teaching accepted as true by a major religious group.
• Dogma: Nonessential Doctrine expected to be believed by members of a particular group within a religion based on its authority.
• Orthodoxy - the essential teachings which must be held by all those who would be accepted as legitimate members of a given religious group.
• Heretical - Any teaching that directly opposes orthodoxy, usually referring to essential doctrines versus dogma.
  It is important to note that, even in Christianity, one might be a heretic without necessarily being unsaved (or even being wrong!). This is a technical and objective term.
• Heterodox (perhaps also Aberrant, Suborthodox, or Unorthodox) - Any teaching that differs from orthodoxy in some significant way, but does not directly contradict orthodox teachings.

So for example in Christianity belief in the Trinity is orthodox and essential. A group who opposes the Trinity (say, Oneness Pentecostals) is heretical. However, someone who believes that Jesus drove a car and lived in a mansion would be heterodox.

Evangelical Christianity would list the following as orthodox doctrine:

1. The Authority, Infallibility, and Inerrancy of the Bible
2. The Tri-Unity of God
3. The Virgin Birth of Christ
4. The Deity of Christ
5. The All-Sufficiency of Christ's atoning sacrifice for sin
6. The physical and miraculous Resurrection of Christ
7. The necessity of Salvation by Faith alone
8. The future physical return of Christ to earth
9. The Eternal conscious bliss of the saved
10. The Eternal conscious punishment of the unsaved

You can now see how a heretic may yet be saved - one can be a heretic on number one above without necessarily compromising the Gospel message.