Clearly the claim to be inspired by the Spirit can and must be tested, for the claim to have the Spirit is not proof that one does. Here spirit has been variously taken to refer to the spirit that inspires the prophet, to the person who is inspired or to the message delivered by the prophet. Obviously the three are related, for in testing a person's words one is actually testing whether or not that person speaks by divine guidance. In light of the rest of the passage two things emerge: First, the author believes that individual persons are inspired or led to confess or deny Christ by spirits, some reality beyond the human individual. Second, ultimately there are only two spirits: God's Spirit, also called the Spirit of truth because it guards and inspires truth (4:2, 6); and the spirit of antichrist, which inspires falsehood, and especially false confession of Christ (vv. 3, 6). The Elder's readers are not to believe every claim to be divinely inspired or to have a prophetic message, but are rather to test the spirits, to discern whether a message is the truth that comes from God.
Such testing is necessary because many false prophets have gone out into the world. While "prophet" in the Pauline literature refers to a specific function within the church (Rom 12:6; 1 Cor 12:10; 14:1-5, 29-33; Eph 4:11), the Johannine epistles refer more broadly to all of those who left the church as false prophets, because they carry with them testimony that claims to be spirit-inspired. That is exactly the point: all persons speak by the inspiration of one spirit or another (Brown 1982:489). Now it falls to the community to discern which spirit guides the teaching of the various individuals whom they encounter. The church must exercise dis cernment, then as now, for truth and error are not always easily distin guished. They do not exist disembodied, but come to us in the shape of real persons with whom we share a variety of relationships. Precisely because "testing the spirits" entails dealing with other persons, perhaps even professed Christians, who claim to be guided by the Spirit, we must exercise care and humility in discerning the truth.
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