Why Is Faith Chosen As An Instrument Of Salvation

"Where were you when I laid the foundation of the earth? Tell me, if you have understanding. (Job 38:4 ESV)

No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him. (John 1:18 KJV)

According to This is Math's Fatal Flaw - YouTube, it is mathematically proven that not everything that is true can be proven. The existence of God is true, but it cannot be proven. No Christian can prove that God exists. The Bible never attempt to prove God's existence. Our belief in God has to be by faith.

But the Word of God, the Bible, is true and can be proven true.

The entirety of your word is truth, each of your righteous judgments endures forever. (Psalm 119:160 CSB)

Jesus said to him, "Have you believed because you have seen me? Blessed are those who have not seen and yet have believed." (John 20:29 ESV)