John 14:17 Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
Truth is not what you believe, it is who you believe.
The most vital of all promises made by God is that special promise to send the Holy Spirit to live in you and lead you in all truth.
John 16:13a Howbeit when he, the Spirit of truth, is come, he will guide you into all truth:
How can you walk in the spirit if you do not have the spirit? It is critical to know the Spirit of Truth for His presence within you is your guarantee of new birth, regeneration, restoration, justification, sanctification and all the promises that come to those who have a saving faith in Christ. He is the power of God unto salvation.
Without the Holy Spirit your faith has not saved you. It was not a saving faith. Even as I write this I know there will be some who will reject the notion that their faith has failed them. It is the nature of man to reject what flies against what he believes. At this moment, if you entertain those thoughts allow me to ask you to be honest about this very thing.
Did you dismiss the thought offhand or did you search your heart for the truth? A man of saving faith will always do a heart check for truth. A man who has convinced himself will rely on his mind, will and emotions. He has done the work, put in the time and deserves to feel good about himself. He is lost in himself and the truth is not in him.