Jamieson, Fausset & Brown

a liar--Greek, "Who is the liar?" namely, guilty of the lie just mentioned (Jo1 2:21). that Jesus is the Christ--the grand central truth. He is Antichrist--Greek, "the Antichrist"; not however here personal, but in the abstract; the ideal of Antichrist is "he that denieth the Father and the Son." To deny the latter is virtually to deny the former. Again, the truth as to the Son must be held in its integrity; to deny that Jesus is the Christ, or that He is the Son of God, or that He came in the flesh, invalidates the whole (Mat 11:27).