Exploring the Meaning of Hairesis in Greek

αἵρεσις means “sect,” a word used for identifiable groupings within Judaism and for the Christian movement as outsiders describe it, and it also appears in moral warnings about internal fracture and destructive teaching. Its nine New Testament occurrences cluster in Acts and then reappear in two apostolic letters where the term is placed in lists of community-threatening realities.

Occurrences

Acts 5:17: “But the high priest rose up, and all those who were with him (which is the sect of the Sadducees), and they were filled with jealousy”

Here αἵρεσις marks an organized party within the leadership sphere surrounding “the high priest.” The parenthetical identification (“the sect of the Sadducees”) frames the subsequent action and emotion: jealousy is located not merely in individuals but in a defined group aligned with particular leadership.

Acts 15:5: “But some of the sect of the Pharisees who believed rose up, saying, “It is necessary to circumcise them, and to command them to keep the law of Moses.””

In this dispute, αἵρεσις identifies a subset within the believing community: “some of the sect of the Pharisees who believed.” The term helps the reader track how inherited group identity continues to shape speech and demands—here, the insistence that Gentile believers must be circumcised and commanded “to keep the law of Moses.”

Acts 24:5: “For we have found this man to be a plague, an instigator of insurrections among all the Jews throughout the world, and a ringleader of the sect of the Nazarenes.”

In accusation, αἵρεσις functions as a label that casts Paul’s association as membership in (or leadership of) a suspect collective: “the sect of the Nazarenes.” The charge gains force from the word’s grouping power: Paul is presented as “ringleader,” and the movement is framed as a defined body capable of fomenting unrest.

Acts 24:14: “But this I confess to you, that after the Way, which they call a sect, so I serve the God of our fathers, believing all things which are according to the law, and which are written in the prophets;”

Paul acknowledges the outsider term without adopting its evaluation. αἵρεσις is the name others apply (“which they call a sect”) to “the Way,” while Paul describes his worship as service to “the God of our fathers” and as belief in what accords with “the law” and “the prophets.” The word therefore appears as a contested classification: it is the label opponents use to categorize a way of life and worship.

Acts 26:5: “having known me from the first, if they are willing to testify, that after the strictest sect of our religion I lived a Pharisee.”

Here αἵρεσις is used from within Jewish self-description: “the strictest sect of our religion.” The term is compatible with an internal taxonomy of commitment and practice. Paul’s point depends on the word’s ability to mark a rigorous, identifiable group (“I lived a Pharisee”) whose reputation could be verified by witnesses.

Acts 28:22: “But we desire to hear from you what you think. For, as concerning this sect, it is known to us that everywhere it is spoken against.”

Late in Acts, αἵρεσις is again the external tag for the Christian movement (“this sect”), paired with the report of widespread opposition: “everywhere it is spoken against.” The word contributes an impression of the movement as a recognizable body with a public reputation, and it frames the listeners’ request to evaluate it by hearing Paul directly.

1 Corinthians 11:19: “For there also must be factions among you, that those who are approved may be revealed among you.”

Although the English renders αἵρεσις as “factions,” the verse’s logic treats it as a real phenomenon within the congregation (“among you”). The word contributes the idea of intra-community grouping that tests and exposes character: the presence of such factional realities becomes the setting in which “those who are approved may be revealed.”

Galatians 5:20: “idolatry, sorcery, hatred, strife, jealousies, outbursts of anger, rivalries, divisions, heresies,”

In this vice list, αἵρεσις appears as one item among relational and communal evils—clustered near “rivalries” and “divisions.” The word’s contribution is to name a form of community-breaking grouping as morally blameworthy, placed alongside other behaviors that fragment relationships and produce conflict.

2 Peter 2:1: “But false prophets also arose among the people, as false teachers will also be among you, who will secretly bring in destructive heresies, denying even the Master who bought them, bringing on themselves swift destruction.”

Here αἵρεσις is not merely a group label but something introduced—“bring in”—and done covertly (“secretly”). The word is qualified as “destructive,” and the verse explains its doctrinal and ethical seriousness by connecting it with “denying even the Master who bought them,” and with a consequent outcome: “swift destruction.” αἵρεσις thus marks a divisive reality that is also bound up with denial and ruin.

Sense and Usage

Across Acts, αἵρεσις consistently serves as a term of classification: it identifies a “sect” within Judaism (“the sect of the Sadducees,” “the sect of the Pharisees”), and it is applied to the Jesus movement as others perceive it (“the sect of the Nazarenes,” “the Way, which they call a sect,” “this sect”). In these courtroom and public-dialogue settings, the word helps speakers place persons and movements into recognizable social categories. That categorization can be neutral and descriptive (as in Paul’s autobiographical reference to “the strictest sect of our religion”), or it can be rhetorically charged (as when a prosecutor portrays Paul as a dangerous “ringleader” and ties him to “insurrections”).

The Acts occurrences also show that αἵρεσις can be a contested label. Paul’s phrasing in Acts 24:14 creates a contrast between what others call “a sect” and how he characterizes his own faith and worship: service to Israel’s God and belief in what is “according to the law” and written “in the prophets.” The word, then, can function as an outsider’s frame for a movement that insiders describe in continuity with ancestral faith. Acts 28:22 adds another dimension: public perception. Calling the movement “this sect” and noting that “everywhere it is spoken against” places αἵρεσις in the realm of reputation and rumor, prompting a desire to hear and judge the movement’s claims firsthand.

In the epistles, αἵρεσις shifts from naming external parties to naming internal threats. In 1 Corinthians 11:19, the term belongs to the lived experience of a congregation (“among you”), where factional groupings become a proving ground that reveals “those who are approved.” The word carries the weight of a community reality that disrupts unity and exposes loyalties. In Galatians 5:20, the placement of αἵρεσις within a chain of relational evils (hatred, strife, jealousies, rivalries, divisions) anchors its sense in social fracture: it belongs to patterns that tear communities into competing camps.

2 Peter 2:1 intensifies the moral and theological stakes by modifying the term as “destructive” and by linking it with denial of “the Master who bought them.” Here αἵρεσις is not presented as a mere sociological subgroup but as something false teachers can “secretly bring in,” with consequences described as “swift destruction.” The word thus encompasses both the formation of a sectarian reality and the propagation of a sectarian teaching that damages the community and imperils those who promote it.

Imagery and Force

The passages collectively give αἵρεσις a concrete social feel: it gathers people into named bodies (“Sadducees,” “Pharisees,” “Nazarenes”) and lets speakers talk about influence, leadership, and reputation. In Acts, the word sits in scenes of official power and public hearing—high priests, accusations, confession, and inquiry—where a movement’s identity is debated and charged. In the letters, the same word belongs inside the community’s moral vocabulary, where “factions,” “divisions,” and “destructive heresies” are portrayed as forces that work among believers and must be recognized for what they do to the life of the church.

Sources: Lexical data from Strong’s Exhaustive Concordance and the Translators Brief Lexicon of Extended Strongs for Greek (STEPBible, CC BY). Occurrence data from the Translators Amalgamated Greek New Testament (STEPBible, CC BY). Scripture quotations from the World English Bible (public domain).