I found it odd that in John 9:30-33, the (healed) blind man refers to scripture, suddenly speaking as a learned scholar to the point where the Pharisees accuse him of lecturing them. I wonder, was it common back in those days, that even the blind and beggars would have thorough understanding of scripture? I assumed only the Pharisees would have such knowledge. To me, this is like a homeless man suddenly getting up and reciting the derivation of the Schrodingers equation to everyone on the street...
The setting here is long before the invention of the printing press. The scriptures were hand copied, thus ordinary people would not have been able to own a copy of the scriptures. However, in ancient Judea during the Second Temple Period, the Jewish scriptures(Christian Old Testament) would have been publicly available in the synagogues to read. In fact, the Jews would go to the synagogue on the Sabbath to hear rabbis read the scripture out loud. Jesus actually does this in Luke 4:16-21.
It is also important to remember that the Torah, Prophets, and Wisdom literature that make up the Christian Old Testament were central to Jewish religion and law during this time. The words of scripture were, as they are now, believed to be inspired by God. With this importance placed on them, it is not a surprise that a man handicapped by blindness would look to the scriptures as an explanation of his ailment as well as a possible source of healing. Thus the blind man had both means and motive to remember the scriptures that he quoted.
John chapter 9 is, in its entirety, a commentary on the claim Jesus makes in John 8:12:
John 8:12: Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life.
The story of the blind man should therefore be read in the context of chapter 9 as a whole. Chapter 9 opens when Jesus sees a man blind from birth and his disciples ask whether the man was a sinner or whether his parents were sinners. Jesus answers that they were not sinners but that the man is blind so that the works of God can be explained, repeating his words from verse 8:12: "
I am the light of the world."
Having spoken, Jesus uses moist clay to anoint the eyes of the blind man then says the wash his eyes in the pool of Siloam, which means 'sending forth'. There follows a long discussion on sin, with the Pharisees saying the man could not really have been blind, because Jesus is a sinner and sinners can not work miracles. The formerly blind man's discourse in verses 30-33 displays a keen understanding of the Hebrew scriptures:
John 9:30-33: The man answered and said unto them, Why herein is a marvellous thing, that ye know not from whence he is, and yet he hath opened mine eyes. Now we know that God heareth not sinners: but if any man be a worshipper of God, and doeth his will, him he heareth. Since the world began was it not heard that any man opened the eyes of one that was born blind. If this man were not of God, he could do nothing.
The Pharisees then accuse him of being born in sin, but now he lectures them.
The meaning of chapter 9 becomes apparent in the final verses of the chapter. First the formerly blind man believes and worships Jesus, to which Jesus explains his mission to the world in terms of blindness and sight, then Jesus tells the Pharisees, who had accused the man of being born blind and altogether in sin, they can see but yet their sin remains:
John 9:38: And he said, Lord, I believe. And he worshipped him.
John 9:39: And Jesus said, For judgment I am come into this world, that they which see not might see; and that they which see might be made blind.
John 9:40-41: And some of the Pharisees which were with him heard these words, and said unto him, Are we blind also? Jesus said unto them, If ye were blind, ye should have no sin: but now ye say, We see; therefore your sin remaineth.
Perhaps the blind man did not know scripture, but John knew scripture. The story of the blind man was an introduction both to the theologically important explanation of Jesus' mission and to his criticism of those who can see but do not believe.