Imagine a father and son stranded on a desert island. There is a small amount of food on the island, just enough to keep them barely alive indefinitely.
The son has limited sailing skill, but the father nonetheless loads their boat with most of the food, and sends the son off in search of rescue.
The father’s action is the manifestation of his faith in his son. Not a proof or a demonstration, a manifestation. It is the father’s faith.
This is the true picture of the atonement. And the son is not Christ. The son is us.