Demetrius hath the witness of all men (Dhmhtriwi memarturhtai upo pantwn). Perfect passive indicative of marturew, "it has been witnessed to Demetrius (dative case) by all." We know nothing else about him, unless, as is unlikely, he be identified with Demas as a shortened form ( Philemon 1:24 ; Colossians 4:4 ; 2 Timothy 4:10 ), who has come back after his desertion or with the Ephesian silversmith ( Acts 19:21 ), who may have been converted under John's ministry, which one would like to believe, though there is no evidence for it. He may indeed be the bearer of this letter from Ephesus to Gaius and may also have come under suspicion for some reason and hence John's warm commendation. And of the truth itself (kai upo auth th alhqeia). A second commendation of Demetrius. It is possible, in view of 1 John 5:6 (the Spirit is the truth), that John means the Holy Spirit and not a mere personification of the truth. Yea we also (kai hmei de). A third witness to Demetrius, that is John himself (literary plural). Thou knowest (oida). "The words in John 21:24 sound like an echo of this sentence" (Westcott). John knew Demetrius well in Ephesus.