But the testimony which these passages bear to the authenticity of this Epistle is not the main reason for their being quoted here. Their interest for us now consists in the light which they throw upon the history of the word "heresy," and upon the attitude of the primitive Church towards heretics.
"Heresy," as Tertullian points out, is a word of Greek origin, and the idea which lies at the root of it is _choice_.[85] Choosing for oneself what pleases oneself, independently of other considerations;--that is the fundamental notion on which later meanings of the term are based. Thus in the Septuagint it is used of a _free-will_ offering, as distinct from what a man is bound to offer (Lev. xxii. 18; comp. 1 Macc. viii. 30). Then comes the notion of choice in reference to matters of opinion, without, however, necessarily implying that the chosen opinion is a bad one. And in this sense it is used quite as often for the party or school of thought which holds the particular opinion as for the body of opinion which is held. In this sense it is several times used in the Acts of the Apostles; as "the _sect_ of the Sadducees" (v. 17), "the _sect_ of the Pharisees" (xv. 5; xxvi. 5): and in this way Christianity itself was spoken of as a "heresy" or "sect"; that is, a party with chosen opinions (xxiv. 5, 14; xxviii. 22). And in profane literature we find Diogenes Laertius in the second or third century speaking of ten "heresies" or schools in moral philosophy (i. 19). But it will be seen from the passages in the Acts that the word is already acquiring somewhat of a bad meaning; and indeed this was almost inevitable, unless the original signification was entirely abandoned. In all spheres of thought and action, and especially in matters of belief, a tendency to choose for oneself, and to pursue one's own way independently, almost of necessity leads to separation from others, to divisions and factions. And factions in the Church readily widen into schisms and harden into heresies.
Outside the Acts of the Apostles the word heresy is found in the New Testament only in three passages: 1 Cor. xi. 19; Gal. v. 20; and 2 Pet. ii. 1. In the last of these it is used of the erroneous opinions themselves; in the other two the parties who hold them may be indicated. But in all cases the word is used of divisions inside the Church, not of separations from it or of positions antagonistic to it. Thus in 2 Pet. ii. 1 we have the prophecy that "there shall be false teachers, who shall privily _bring in_ destructive _heresies_, denying even the Master that bought them." Here the false teachers are evidently inside the Church, corrupting its members; not outside, inducing its members to leave it. For the prophecy continues: "And many shall follow their lascivious doings; by reason of whom the way of the truth shall be evil spoken of." They could not cause "the way of the truth to be evil spoken of," if they were complete outsiders, professing to have no connexion with it. In Gal. v. 20 "heresies" are among "the works of the flesh" against which St. Paul warns his fickle converts, and "heresies" are there coupled with "factions" and "divisions." In 1 Cor. xi. 19 the Apostle gives as a reason for believing the report that there are divisions in the Church of Corinth the fact that (man's tendency to differ being what it is) divisions are inevitable, and have their use, for in this way those which are approved among Christians are made manifest. It is possible in both these passages to understand St. Paul as meaning the "self-chosen views," as in the passage in 2 Pet., rather than the schools or parties which have adopted the views. But this is not of much moment. The important thing to notice is, that in all three cases the "heresies" have caused or are tending to cause splits inside the Church: they do not indicate hostile positions outside it. This use of the word is analogous to that in the Acts of the Apostles, where it represents the Pharisees and Sadducees, and even the Christian Church itself, as parties or schools inside Judaism, not as revolts against it. We shall be seriously misled, if we allow the later meaning of "heresy," with all its medieval associations, to colour our interpretation of the term as we find it in the New Testament.