God speaks and acts through revelation, most particularly through Jesus Christ, the incarnate Word (John 1:1, 14) and the Scriptures, the written Word of God. God has uniquely chosen to disclose himself through these two means. The truth of the gospel is found in God's self-revelation which finds its fulfillment in Christ (Acts 4:12) who proclaimed and taught the gospel faithfully and who was crucified, buried, and resurected to save us from our sins, restore our relationship with God, and give us eternal life.
Unfortunately, our sin blinds us to the truths of the gospel and prevents God's revelation from being understood properly, but the Holy Spirit has the power to illuminate our minds and open our hearts so that the believer can understand the Word of God and the gospel promises. The Holy Spirit communicates and directs the divine word to our sinful minds and hearts in ways that help the Scriptures become alive and meaningful. He enlightens our finite minds and motivates our stubborn wills to the reality and truth of the gospel message. There is no benefit unless the Holy Spirit shines his light upon the text and brings life and power to the Word of God (2 Corinthians 3:6). The Holy Spirit, being the author of the text, is absolutely required to bear witness to and authenticate the veracity of the Holy Scriptures. He penetrates our hearts and minds and persuades us that the Scriptures are the Word of God.
J.I. Packer explains: The mark of this understanding is that Scripture now appears coherent: To the man enlightened by the Spirit, Scripture is no longer a bewildering jumble of isolated items, as it may well have seemed to him before, but under the benefit of this assistance all the parts of the Scripture, in their harmony and correspondency, all the truths of it in their power and necessity, come in together to give evidence one to another, and all of them to the whole.