A simple question, but probably the most important one a person can answer in their lifetime. For from the answer of this question, one's whole life's philosophy, lifestyle,and world-view flow from the realms of philosophical or theological theory into practical application of living everyday life.
Pilate's famous question, "What is truth?"
The Bible gives 3 definition of what is truth.
1. Your righteousness is an everlasting righteousness,And Your law is Truth. ~Psalm 119:142
2. Sanctify them by the truth; your word is Truth. ~John 17:17
3. Jesus said to him, “I am the way, the Truth, and the life. No one comes to the Father except through Me." ~John 14:6
Recap, what then does the Bible say: The Law, The Word, and Jesus is Truth.
So, as Jesus said in the same conversation with Pilate's question, "you are right in saying I am a king. In fact, for this reason I was born, and for this I came into the world, to testify to the truth. Everyone on the side of truth listens to me." (john 18:37).
May we all side with and listen too the Truth!