"If we accept the testimony of human witnesses, God's testimony is greater." (1 John 5:9)
We accept the testimony of human witnesses every day.
We accept what our doctors tell us about our health.
We accept what the government tells us about the state of the economy.
We accept weather reports.
We accept what advertisers tell us about their products.
From the above, it appears as if man is naturally a trusting being.
"If we accept the testimony of human witnesses, God's testimony is greater." (1 John 5:9)
God's word is worthy of greater trust because it is more certain.
"The law of the Lord is perfect, refreshing the soul.
The decree of the Lord is trustworthy, giving wisdom to the simple." (Psalm 19: 8)