We'll begin by assuming that there is truth and that it can be known.
How could we have a conversation, otherwise?
How would I know what decision to make when I face one of life's constant dilemmas? Whose advice to follow?
Here is a thing which is not true: "Just follow your heart."
What if my heart is deceitful above all things and desperately wicked? I shudder to think of all the places my heart has led me.
The selfish deeds I have performed and the hurt I have caused "just following my heart."
What an incredibly selfish little organ my heart is! Still, perhaps you don't have that problem? Look deep and long before you answer.
So if "every inclination of my heart is only evil, all the time," where will I look for truth?
For the Christian there's a ready answer. There is a God who speaks to his children. We are told that Jesus is the Living Word of God. There is also a written Word. If I believe in God, do I accept Him at His word? That His Word is true? How could I do otherwise?
If God tells me He is perfectly righteous, I must believe Him. If He tells me I must be righteous too, I go "How?" There's this problem of the heart remember? Back I go to the Word.
Which reminds me of the Living Word: God's Only Son, God in the flesh, Jesus. He's already lived a life of righteousness. I can have this righteousness credited to me if I believe on His Name. Better that that: this faith is free! A gift from God.
So how about this: what if I just say I believe in Jesus? I don't have to do any of this righteous stuff, right? Hmmm.
Back to the written Word where I read that a heart changed by Jesus' perfect love will want to do this righteous stuff; will actually be broken when I fail to live up to God's standards and fly to Him begging forgiveness.
So I bow to the authority of God's Word. And the Truth I find there. Especially those parts about my heart (Jeremiah 17:9; Genesis 6:5).
What about the non-believer? Mercifully, God has a Truth for you as well: repent and be saved (Acts 3:19). I'm praying