In John 14.16-17, Jesus says to his disciples,
I will ask the Father and he will give you another Advocate to be with you forever. This is the Spirit of truth, whom the world cannot receive, because it neither sees him nor knows him. You know him, because he abides with you, and he will be in you.
Those who believe in Jesus have been given an "Advocate," the Holy Spirit. The Greek word that the NRSV translates as "Advocate" is sometimes brought into English as "Paraclete."
The Paraclete
In 14.6 Jesus states, "I am the way, and the truth, and the life." In 8.31-32 we read, "Then Jesus said to the Jews who had believed in him, 'If you continue in my word, you are truly my disciples; and you will know the truth, and the truth will make you free.'" Similarly, in 18.37 Jn tells us, "Pilate asked him, 'So you are a king?' Jesus answered, 'You say that I am a king. For this I was born and for this I came into the world, to testify to the truth. Everyone who belongs to the truth listens to my voice."

There is a significant correlation between Jesus' role on earth and the role of the Paraclete.

In 16.12-15 Jesus states,
I still have many things to say to you, but you cannot bear them now. When the Spirit of truth comes, he will guide you into all the truth; for he will not speak on his own, but will speak whatever he hears, and he will declare to you the things that are to come. He will glorify me, because he will take what is mine and declare it to you. All that the Father has is mine. For this reason I said that he will take what is mine and declare it to you.
The work of the Paraclete mirrors the work of Jesus. We might say that Jesus is the first Paraclete, and the Holy Spirit is the second Paraclete.

This is one reason that there is less of an eschatological emphasis in Jn's gospel than in the Synoptics. The necessity of Jesus' return is diminished because the Paraclete continues Jesus' work on the earth.
It seems that Jn believes his gospel to reflect not only the story of Jesus, but the teachings of the Paraclete. The Johannine community's understanding of Jesus changed after his death because of the Paraclete's teaching. For example, in 14.25-6 Jesus states, "I have said these things to you while I am still with you. But the Advocate, the Holy Spirit, whom the Father will send in my name, will teach you all that I have said to you." Similarly, in 16.12 Jesus tells his disciples, "I still have many things to say to you, but you cannot bear them now. When the Spirit of truth comes, he will guide you into all the truth…."
Bassler, Jouette. Lecture on the Gospel of John, 11/18/00. Southern Methodist University, Dallas, TX.
Ehrman, Bart D.
The New Testament: A Historical Introduction to the Early Christian Writings,
2nd ed.
New York and Oxford: Oxford UP, 2000.
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