'Sanctify them by the truth; your word is truth.' John 17:17
In the garden at the end of His days with the twelve Jesus spent very intense and very intentional time in prayer. Praying that His disciples would be 'set apart for noble purposes' defined by truth. Truth does exist. It isn't subjective. It isn't private nor individual. It's universal. Eternal.
And it's found in the word. Scripture. The very word God spoke through His prophets of whom Jesus was the greatest.