Taking the protestant principle to heart, we next turn to the Bible — what kinds of heretical doctrine does it discuss and forewarn us about? The Bible makes frequent reference to false teachings and it is often within the context of refuting heresy that its positive doctrinal material is cast.

The Old Testament contains solemn warnings against anyone who prophesies or proclaims teachings in the name of any god but the LORD, Jehovah (Deut. 13:1-5; 18:20-22). This is the assumed context in which the New Testament teaching about heresies is framed.

In the New Testament, there are warnings about false prophets (Matt. 24:11, 24; 2 Pet. 2:1) — that is, those who make predictions in the name of God and whose predictions turn out to be false (cf. Deut. 18:22). There is also a warning about false apostles (2 Cor. 11:13). There are warnings about those claiming to be the Christ, or claiming that Christ has come, or that the Day of the Lord has come, or that the resurrection has occurred — when all these events will be so plain and conspicuous that no one will miss them (Matt. 24:5, 23-27; 2 Thess. 2:1-2; 2 Tim. 2:16-18).

There are also warnings about those who proclaim another Jesus or a different gospel, or who introduce a spirit other than God's Spirit (1 Cor. 15:3-5; 2 Cor. 11:4;
Gal. 1:6-9). The teaching that circumcision and keeping the Law are necessary for salvation is condemned (Gal. 5:2-4; Phil. 3:2). On the other side, teaching that liberty in Christ gives us excuse for licentiousness is also condemned (Jude 4).

The denial of Jesus Christ's coming in the flesh is regarded as from the spirit of antichrist (1 John 4:1-6). There are warnings about people who cause dissensions by teaching doctrine directly opposed to what Christians already know to be true (Rom. 16:17; Tit. 3:10-11). There are warnings about those who claim to love God but do not love God's people (1 John 4:20; 5:1), and who deliberately break away from the church on the basis of perverted doctrine (1 John 2:19). Finally, there are warnings against adding to or taking away from the words of prophetic Scripture (Rev. 22:18-19) or twisting the Scriptures (2 Pet. 3:16).

Looking over these warnings from Scripture, we may classify heresies into six major categories:

1. Heresies about revelation — teachings that distort, deny, or add to Scripture in a way that leads people to destruction; false claims to apostolic or prophetic authority.
2. Heresies about God — teachings that promote false gods or idolatrous distortions of the true God.
3. Heresies about Christ — denials of His unique Lordship, His genuine humanity, His true identity.
4. Heresies about salvation — teaching legalism or licentiousness; denying the gospel of Christ's death and resurrection; and so forth.
5. Heresies about the church — deliberate attempts to lead people away from the fellowship of true Christians; utter rejection of the church.
6. Heresies about the future — false predictions for which divine authority is claimed; claims that Christ's return has taken place; and the like.

Note that errors in any one of these six categories tend to introduce errors into the other five. Take, for instance, the heretical view held by many groups that the church became totally apostate in the early centuries and thus had to be "restored" in the last days. This doctrine implies (1) that Scripture is not a sufficient revelation, but needs supplementing or "explaining" by some authoritative teacher or publication. It also almost always serves as a basis for rejecting the early church's views of (2) God and (3) Christ. Since the Reformation is rejected as falling short of the needed restoration, (4) the doctrine of salvation by grace through faith is likewise rejected. And the doctrine of a restoration comes to dominate the group's views of (5) the future, as it requires them to view many or most biblical prophecies about the future as finding fulfillment in their own group.

We find then that an error in any area of doctrine can affect every other area. Therefore, although heresies tend to fall directly into one or more of these six major categories, heresies can in fact occur on virtually any doctrinal subject. For example, someone who teaches that angels should be worshipped is teaching a heretical view (Col. 2:18), even though the subject matter is angels. This is because worship of any creature completely cuts the heart out of any confession of God as the one God.

Nor should it be thought that the New Testament gives us a complete catalogue of all possible heresies. In our day there are literally thousands of clever distortions of Christian theology that deserve the label heresy, and they can be seen as such apart from being explicitly anticipated and identified as heretical in the Bible. The Bible teaches us what is absolutely essential, enunciates principles as to what is basic to sound Christian faith and what is nonessential, gives us a wide variety of examples of heresies, and expects us to exercise discernment in evaluating new and controversial teachings when they surface.

Furthermore, it must be realized that as the church progresses through history and deepens its understanding of Scripture, heresies in general are becoming more subtle, more deceiving, more easily mistaken for authentic Christianity.

For example, modern-day heretics who reject the Old Testament are rarely as frank about it as the second-century heretic Marcion, who simply denied that the Old Testament was in any sense Scripture (he also discarded much of the New Testament). Instead, they adopt a method of interpretation which, while formally admitting that the Bible is God's Word, in effect makes the Old Testament irrelevant to the Christian, which is contrary to the clear teaching of the New Testament (Rom. 15:4;
2 Tim. 3:16).

In short, heresy is any doctrine which the Bible explicitly labels as destructive, damning error; or a doctrine which the Bible instructs is not to be tolerated in the church; or any doctrine which, even if not mentioned in the Bible, utterly contradicts those truths which the Bible indicates are essential for sound Christian faith.

Aberrational views can also be classified according to the above six categories. In each case, the aberrant doctrine seriously compromises the Bible's essential teaching in one or more of those six areas, although not outright denying it. For example, the practice of speculating on the precise date of the return of Christ can often be an aberration that stops short of heresy. The practice is certainly unbiblical, and in the context of heretical systems of doctrine such date-setting can itself be regarded as heretical. But in some cases, teachers have argued more modestly that Christ might return on a certain date, admitting the very real possibility of error, and urging only intensified obedience to God's Word. Even this sort of teaching should be regarded as more or less aberrant, since it compromises the biblical warnings against making predictions of this sort; but it is not of itself heretical.