If Abraham had refused to take Isaac up the mountain and followed God's instructions, his refusal would be an outward display of inward rebellion. If Rahab had turned away the spies, her actions would have been a clear statement of trust in her own government to rescue the city.
Humans are destined to act on their beliefs. If we honestly believe God is actively involved in our lives, we will make our decisions based on his word to us. If God is an idea to us, but we do not truly believe that he cares about us as individuals we will naturally be guided by our desires.
The outcome of either belief is eternally significant (James 2:21-26).
