Paul (Saul of Tarsus before his conversion) tracked down Christians by relying on networks, official authorizations, and investigative methods typical of the period — not on any “reading of hearts.” The key sources are Acts 7–9, 22, and 26.
- Legal authority and letters of commission: The high priest and the gave him letters to arrest “those who call on the Name” in the , in Damascus as in Jerusalem (Acts 9:1–2; 22:5). These warrants opened local doors for him and gave the arrests legal legitimacy.
- Spotting people in the : The first Jewish Christians still attended the ; Paul “searched” for men and women “of the Way” where they prayed and gathered (Acts 9:2; 26:11). Speaking about Jesus, praying “in the Name,” and baptisms made these groups identifiable.
- Denunciations and rumors: The religious authorities relied on informers, complaints, and public reputation. After Stephen’s death, “a great persecution” broke out and the community became known; Paul went “from house to house” arresting believers (Acts 8:1–3). This implies lists of residences obtained through denunciations or surveillance.
- Interrogations and pressure: Paul admits that he “forced them to blaspheme” and punished them in the to make them renounce their faith (Acts 26:10–11). These interrogations brought other names and networks to light.
- Pursuit beyond the city: He did not limit himself to Jerusalem; his letters also targeted communities that had taken refuge in Syria (Damascus), proof of coordination between cities (Acts 9:1–2).
On the question of Christians “in secret”: some probably sought discretion to avoid prison, but the movement remained visible through:
- regular meetings (houses, ),
- public acts (baptisms, almsgiving),
- a recognized label (“the Way,” “those who call on the Name”).
Even secrecy had its limits in close-knit communities where rumor circulated.
In short: Paul identified Christians through access to the , denunciations, the reputation of the groups of “the Way,” house-to-house searches, and letters of authorization that allowed him to arrest and interrogate, which exposed other members.