If you demanded an one word answer on this question, it would be “Jesus.” Of course, there is “another Paraclete” (Jn 14:16), who is the Holy Spirit, as they told you in your Sunday school and well, they were right. But for this moment, let us embrace another perspective on the same thing.
Imagine that you have a double-sided mirror with two persons standing on both sides. Now imagine that both sides reflect that person and both sides are mirrored by each other. After a short while you realize that appearance, facial expression, moves, words, thoughts and intentions of those two are indistinguishable. Yet you know that one is on the left and one is on the right and that they are essentially two persons that impersonate each other.
(1) John 14:6. There are two Paracletes in the Gospel of John. The present one and the promised one. The present one defines Himself as “the way, and the truth, and the life” (Jn 14:6). But the promised one teaches (14:26) and reveals (15:26) too, thus showing the way. The promised is called the Spirit of truth three times (14:17; 15:26; 16:13), so we suspect with Raymond E. Brown that the promised one is the Spirit of truth because “in Johannine thought the Paraclete is the Spirit of Jesus and Jesus is the truth.”1 The promised one also gives life (6:63). Of course, the present one and the promised one are two different persons. If Jesus is the way, the Paraclete teaches Jesus on the way of faith. If He is the truth, the Paraclete is Spirit of the truthful Gospel who speaks “not on his own” but on behalf of Jesus (16:13). If Jesus is life, the Paraclete distributes Jesus to people of all time on regeneration.
(2) John 7:39 and 16:7. Jesus had to go away in order to let the Paraclete come (16:7). But why couldn’t he call him to come earlier? It is because of Paraclete’s role. Brown suggests that “the Paraclete is the presence of Jesus when Jesus is absent.”2 The Paraclete simply provides Jesus for us where we need Him. This applies particularly to two important tasks that Jesus was doing while walking on the Earth and that He no longer does as He is in the heaven. Firstly, as George L. Parsenios suggests, 1 John 2:1 describes Jesus as our Paraclete in a forensic sense similar to Hebrews 7:24f, because he intercedes for us before God. But judging from John 7 and 8, Jesus’ earthly task was not that of an advocate but that of a prosecutor. Thus the Paraclete continues Jesus’ “legal battle against the world.”3 Secondly, as A. R. C. Leaney observes in John 15:26, the Paraclete “helps those who preserve the tradition of the historical Jesus by witnessing to the reality of the Christ in his Church.”4 Leaney suggests that in spite of peculiarity of Johannine background, the Paraclete represented the experience of Christ’s presence in the Church.5 The Paraclete is guarantee of this presence. As Calvin wrote, the Spirit “retains and fixes our faith on him alone, that we may not seek elsewhere any part of our salvation.”6 Christ is something that everyone in the church must have experienced. And the Paraclete is the exclusive provider of this experience.
(3) John 14:9 and chapter 21. The Disciples will recognize the Paraclete as if it was Jesus (Jn 14:9).7 In John 14:18 Jesus says to the disciples that he “will not leave [them] orphaned” and in immediate context of verse 20 He adds, “On that day you will know that I am in my Father, and you in me, and I in you.” When Jesus was crucified, the disciples found themselves confused, least to say. Peter, the Zebedees and some more went fishing. They didn’t seem to know what to do and Jesus had to revisit them and urge them again, “Follow me!” (Jn 21,19). But in Acts 2 when the Paraclete has fully come, as we claim, confusion was replaced with absolute certainty. Peter’s prophetic speech before curious crowds on the day of Pentecost suggest that he knew for certain that this is not result of their bad sleep, nor of hunger caused by their primitive christian communism, but that “The Comforter has come.”
So, this is my perspective on the Paraclete in the Fourth Gospel. In the follow-up, I'll propose what I think Pentecostals could learn from this reading of John.