How is truth defined?
Truth is rooted in the eternal God who’s all powerful and unchangeable. Jesus prayed, “Sanctify them by the truth; Your word is Truth” (John 17:17).
Truth is far more than facts. It’s not just something we act upon. It acts upon us. We can’t change the truth, but the truth can change us. It sanctifies (sets us apart) from the falsehoods woven into our sin natures.
As Christ the living Word is truth, so his written word is truth. Though heaven and earth will pass away, God’s truth never will.
Over half the New Testament uses of “truth” (aletheia) are in John’s gospel. Truth is reality. It’s the way things really are. What seems to be and what really is are often not the same. As I develop in my novel Deception, “Things are not as they appear.” To know the truth is to see accurately. To believe what isn’t true is to be blind.
God has written His truth on human hearts, in the conscience (Romans 2:15). Shame and twinges of conscience come from a recognition that truth has been violated. When the world hears truth, if spoken graciously, many are drawn to it by the moral vacuum they feel. The heart longs for truth—even the heart that rejects it.
As followers of Christ, we are to walk in the truth (III John 3), love the truth, and believe the truth (II Thessalonians 2:10, 12). We’re to speak the truth “in love” (Ephesians 4:32).
Truth is far more than a moral guide. Jesus declared, “I am the way, the truth and the life; no man comes to the Father but by Me” (John 14:6). He didn’t say He would show the truth or teach the truth or model the truth. He is the truth. Truth personified. He is the source of all truth, the embodiment of truth and therefore the reference point for evaluating all truth-claims.
For more on the subject of grace and truth, see Randy Alcorn's book, The Grace and Truth Paradox.