Matthew 20:29, Mark 10:46-47 Why add a blind man?

I think Matthew just changed it to fit better with the two brothers of Zebedees. The parallel in Mark is largely that of the blind seer. The idea is that the apostles are dumb as a sack of hammers and don't see that Jesus is the Messiah. But, the blind man without eyes proclaims him "son of David" and asks to be healed and then follows him. Whereas the Apostles see with their eyes him feeding thousands and do not see at all. In the Odyssey the blind seer warns Odysseus of the suffering to come as he returns home. Here we have Jesus just before the passion.

It was a pretty common theme in many Greek myths that the blind seer would see what the seeing people could not. In Oedipus it's followed by the extra irony of him blinding himself after the seer's prophecy came true. Here Jesus keeps doing miracles extremely giant miracles and the apostles don't understand no matter how many times they are told. But, the blind man instantly knows and completely understands.

The change that Matthew made goes less towards the allusion to the Greek myth and more directly parallels the brothers of the Zebedees who just before are asked to sit at the right and left of Jesus. And Jesus says that that isn't up to him. Then Jesus heals the two blind men who follow him without ambition and see what the apostles cannot. One presumes they follow him on the right and left to Jerusalem, and towards the coming passion.

Rather than just an unassociated blind seer that basically is cribbed from Homer. We get phantom parallel and reversed James and John (Zebedee). The apostles are see but are blind to the truth. They ask for honors that are not earned. The blind men cannot see but already know the truth. And they follow, where the apostles shall scatter.

It really is brilliant mythology.

Anti-suffragette's argument.

"A stranger from another planet, ... would certainly be led to believe that Christians are, and always have been, unable to tolerate so cruel and inhuman an institution. It is even suggested that it was the Church of Christ which finally abolished this unholy practice. Christianity abolish slavery! Why, slavery was maintained under Christianity for over eighteen hundred years; while in America after all those centuries a Christian people fought a bitter and bloody war, lasting four long years, and suffered the loss of a millions of men and money before they would give it up!" - Mrs. John Martin (1910)