John Calvin Commentary Mark 8:24

"And he looked up, and said, I see men; for I behold [them] as trees, walking." — Mark 8:24 (ASV)

I see men. Our Lord had put the question to the blind man for the sake of his disciples, to inform them that the man had received something, but that until now nothing more than a slight beginning of the cure had been achieved.

The reply is that he sees men because he perceives some persons walking who are upright like trees. By these words, he acknowledges that his sight is not yet so clear as to distinguish men from trees.

But he has already obtained some power of seeing, because he conjectures from the motion that those whom he perceives to be in an erect posture are men; and it is in this respect that he says they are like trees. We see then that he speaks only by conjecture when he says that he sees men.