When he was alone, the Twelve and the others around him asked him about the parables. He told them, “The secret of the kingdom of God has been given to you. But to those on the outside everything is said in parables so that,
“‘they may be ever seeing but never perceiving,
and ever hearing but never understanding;
otherwise they might turn and be forgiven!’”
Mark 4:10-12 NIV
When Jesus disciples ask him about a parable he had just told, the Sower and the Seed, he responded with the quote above. He tells his disciples that he is telling parables to prevent those on the outside from being able to comprehend his teaching and turn to him. And that seems pretty strange to me. Why would he say that? Does he not want everyone in the world to turn to him and be saved? Is he trying to prevent some from knowing who he is?
I have struggled with this passage every time I have read it because it seems so contrary to what I understand God is doing. But is it really? What does God want from me? The scripture clearly says that my response to him needs to be based upon faith. When he comes to me, like he did the twelve in the gospels, and says "follow me", will I follow him wherever he goes? Or will I expect him first to offer me rational argument and convincing proofs.
Those to whom the parables were explained were the one who had responded to Jesus call. The ones on the outside were those who had gathered around because Jesus was feeding them and healing them; not bad motives necessarily, but not what is expected. They had seen the miracles and had heard him teach, but they were still on the outside; they had not committed to him. And Jesus was unwilling to give them any more in depth teaching. He was not going to 'argue' them into the kingdom. If they are going to see and hear without a faith based response, then they are not what he wants.
The spiritual truths, or secrets of the Kingdom, belong to those who are citizens of God's kingdom, not to outsiders. And Jesus shares them in a way that enables Kingdom citizens to understand while also preventing understanding by outsiders.