Is truth relative or Absolute?

Read Proverbs 14.

Nothing is more foundational to a person's character that truthfulness.  If one's words cannot be trusted then any relationship with them will prove futile and, perhaps, dangerous.

1. Living a lie. (v.2)
How a person responds to the LORD is the first step in building a life of truthfulness.  It is the understanding that we are accountable to God for every word.  Jesus said,  "I tell you, on the day of judgment people will give account for every careless word they speak." (Matthew 12:36)  Those who try to ignore this basic truth will find themselves living a lie, pretending they have no accountability.  With God as Judge, no one gets away with lying.  

2. Telling a lie. (vv.5 and 25)
Both of these verses refer to a witness providing public testimony.  The example in verse 25 appears to be a capital trial where a defendant's life is at stake.  The point is that what we say has direct effect on the lives of others.  Always telling the truth is the recognition that our words are accountable to others.  Sooner or later, the truth will be known.  No one gets away with lying.
  
3. Knowing the truth. (v.6)
When a person is right with God they are committed to the truth.  Understanding the applications of truth is the essence of spiritual growth.  Sid S. Buzzell wrote, "Mockers look for wisdom in all the wrong places." (Bible Knowledge Commentary).  Some are being told the lie to look within themselves.  Some are told the lie to trust in systems or organizations.  The Apostle Paul wrote strong words of condemnation for those who would seek truth in other places in 2 Timothy 3:  The entire chapter makes the point that without a commitment to Jesus Christ and the Scriptures one is doomed to "always learning and never able to arrive at a knowledge of the truth." (v.7)

Jesus, the Living Word of God.  "I am the way, the truth, and the life.  No one comes to the Father except through me." (John 14:6)
The Scriptures, the Written Word of God.  Jesus prayed, "Sanctify them in the truth; your word is truth." (John 17:17)