In relating the events surrounding Peter’s difficult visit to Antioch, Paul utters a strong statement about Peter’s moral standing on the issue of his behavior vis-à-vis table fellowship with Gentiles. Paul opposed Peter to his face before the entire assembly “because [Peter] had condemned himself” (ὅτι κατεγνωσμένος ἦν). Unpacking the force of this expression requires attention to both lexical and grammatical details. Concerning the lexeme, in the classical period the verb καταγινώσκω regularly carried technical legal denotations of charging someone with a crime or pronouncing a guilty verdict; see Deut 25:1 in the LXX for a similar use. Other occurrences in the LXX and Koine period, however, involve not a legal, public context but a personal, private one. See, for example, Sir 14:2: μακάριος οὗ οὐ κατέγνω ἡ ψυχὴ αὐτοῦ. The other two uses in the NT (1 John 3:20, 21) are certainly in this personal vein. So the first lexical question is whether the legal or personal meaning is in view. Given the preceding context in Gal 2:1-10, in which the private meeting in Jerusalem resulted in a formalized decree or agreement about the acceptability of Paul’s gospel and how Paul and the Jerusalem apostles (of which Peter was one) would divide their labors, and in light of the following context in which Paul makes the case that Peter’s public actions in Antioch deserve censure because they were in some sense contradictory to the gospel, the public, legal meaning of “to pass sentence, to condemn” makes much more sense in Gal 2:11. We need not assume, though, that Paul was actually taking on legal authority of some kind over Peter in this declaration; very likely Paul is speaking metaphorically, using technical, legal language to drive home the inappropriateness of Peter’s behavior. Concerning the grammar, there are two issues to address: the function of the participle and the function of its voice. As a participle, the collocation with a conjugated form of εἰμί means that this participle is periphrastic. The imperfect of εἰμί with the perfect participle denotes the pluperfect periphrastic tense; this makes excellent sense after the aorist main verb of the preceding independent clause as this action of Peter’s self-condemnation occurred earlier in time, before Paul opposed him to his face; as the ὅτι here indicates, this condemnation is the grounds for Paul’s public rebuke of Peter. As to the voice, the spelling of the participle could be either middle or passive. The passive is more common than the middle as a whole in the NT, but there is no clear indication from the context who would be the agent of this action. If the participle is understood as middle, then clarity is immediately obtained: With his own actions Peter condemned himself, especially in light of the prior context of the Jerusalem meeting which in Paul’s mind settled the issue of Jew-Gentile relations in the church.