1 tn After a verb of perception (the participle ὁ πιστεύων [Jo pisteuwn]) the ὅτι (Joti) in 5:5 introduces indirect discourse, a declarative or recitative clause giving the content of what the person named by the participle (ὁ πιστεύων) believes: “that Jesus is the Son of God.” As in 4:15, such a confession constitutes a problem for the author’s opponents but not for his readers who are genuine believers.
2 tn This ὅτι (Joti) is best understood (1) as causal. Some have taken it (2) as declarative, giving the content of the Spirit’s testimony: “and the Spirit is the One who testifies that the Spirit is the truth.” This is certainly possible, since a ὅτι clause following the cognate verb μαρτυρέω (marturevw) often gives the content of the testimony (cf. John 1:34; 3:28; 4:39, 44). But in the Gospel of John the Spirit never bears witness on his own behalf, but always on behalf of Jesus (John 15:26, 16:13). There are, in fact, some instances in the Gospel of John where a ὅτι clause following μαρτυρέω is causal (8:14, 15:27), and that is more likely here: “and the Spirit is the One who testifies, because the Spirit is the truth.”