Simple. This man was blind from birth, then he could see. Once one has gone from darkness to light, it is simple: " Lord, I believe."

John 9:35-38

Jesus heard that they had cast him out, and having found him he said, “Do you believe in the Son of Man?”
He answered, “And who is he, sir, that I may believe in him?”
Jesus said to him, “You have seen him, and it is he who is speaking to you.”
He said, “Lord, I believe,” and he worshiped him.
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