The man in the story had no demon, no disease that caused his blindness. He was born blind. Other healers and prophets had been able to cure blindness, but The Master would bring sight to one born blind, something never before achieved, and a demonstration that there was something different about Him, that the power of God was available to Him on demand.

Now it is apparent that no-one but The Master, the blind man, and we readers know of the actual miracle. The Pharisees had only anecdotal evidence that there even was such a miracle.