Answer
In John 14:17, Jesus says, “Even the Spirit of truth, whom the world cannot receive, because it neither sees him nor knows him. You know him, for he dwells with you and will be in you” (ESV). Because the ESV capitalizes Spirit, modern readers can easily infer that the spirit in question is the Holy Spirit. To understand why Jesus refers to the Holy Spirit as the “Spirit of truth,” let us review the context of John 14.
John 14 is part of the Upper Room Discourse (John 13—17), a collection of teachings delivered by Jesus to His disciples on the night before His crucifixion. In these final moments, the disciples were greatly distressed about the impending departure of their beloved friend, Jesus (John 14:1). For this reason, Jesus took an extended moment to calm their troubled hearts and reassure them that “another Helper” was on the way (John 14:16, ESV).
The Greek term translated as “Helper” (John 14:16, 26; 15:26; 16:7) is paráklētos. The form of this word is passive and means “one who is called alongside.” At the Son’s request, the Father will send another Helper to encourage and exhort the disciples.
John’s use of the term another implies that the disciples already had a helper—the one who would soon depart from the earth. Although the Gospel writers never explicitly refer to Jesus as a paráklētos, the term is applied to Him in 1 John 2:1. Thus, in the context of John 14:16, Jesus promises to send His disciples a helper of the same type, and that helper would continue the ministry that Jesus began.
In John 14:17, the identity of the helper is now revealed: He is the Spirit of truth (cf. John 15:26; 16:13). The Spirit of truth is God the Holy Spirit, the third Person of the Trinity. The Father will send the Spirit to come alongside the disciples. He is called the Spirit of truth because He bears witness to the truth of Jesus Christ (see John 14:6).
In contrast to the work of the Holy Spirit is the work of the devil, a being who does not hold “to the truth, for there is no truth in him. When he lies, he speaks his native language, for he is a liar and the father of lies” (John 8:44). Because the unbelieving world remains ensnared by satanic falsehoods, they cannot receive the Spirit of truth (cf. 1 Corinthians 2:14). Tragically, unbelievers prefer to walk by sight and not by faith, failing to understand that sight guarantees nothing.
At the moment of His baptism, Jesus received the Holy Spirit: John bore witness: “I saw the Spirit descend from heaven like a dove, and it remained on him” (John 1:32, ESV). So, in a sense, the Spirit of truth was already with the disciples. Following the departure of Jesus, however, the disciples will know the Spirit more intimately because He would be in them (cf. Romans 8:9–11 and Ephesians 1:13–14).
Before the disciples began their ministry, Jesus instructed them to remain in Jerusalem for the promised Holy Spirit: “And while staying with them he ordered them not to depart from Jerusalem, but to wait for the promise of the Father, which, he said, ‘you heard from me; for John baptized with water, but you will be baptized with the Holy Spirit not many days from now’” (Acts 1:4–5, ESV). Once the Holy Spirit came upon them, they were fully equipped to proclaim the gospel of Jesus Christ (verse 8).
Believers should be thankful that the Spirit of truth is with us, in us, and upon us. For, without His guidance and light, we could not distinguish truth from error.
