Jesus is very clear that his disciples have been given the secrets of the kingdom of heaven, while others among the crowds may not have been given these secrets. This brings two questions to mind: 1) what are the secrets? and 2) why would Jesus teach some the secrets and not others?
As for the first question, the central secret is that we each have an eternal loving relationship with God, should we choose to return home to Him and embrace this relationship. This is the secret of the kingdom of heaven. God's kingdom is a place of love. It is a place of loving relationships and loving service. God did not create us to be his slaves. He created us to exchange confidential loving relationships with. The 'service' being spoken of in scripture is the type of service that is done when one person loves another. This means of course, that we have the freedom to love Him or not. Without freedom there is no question of real love. The fact that we are now away from the kingdom of heaven means that we are among those who have chosen not to love God. We are among those who have decided that we would rather play 'god' than love God. This is the central secret of the kingdom of heaven that Jesus taught. The central component was stated clearly by Jesus:
“Love the Lord your God with all your heart and with all your soul and with all your mind.” (Matt. 22:37)
As to the second question, these 'secrets' are secrets not because they are not being offered to everyone, but because most refuse to hear the teachings and take them into their hearts.
There are many examples of this, as Jesus’ teachings have been bent and twisted into meanings that Jesus never intended. How could this happen, one might ask? Jesus’ words themselves are plain and he uses various analogies and parables to explain them. How could people interpret Jesus’ statements in so many different ways?
This is because they do not want to hear Jesus’ teachings. They do not want to see the Truth that he spoke of. They are simply focused upon things he said that serve their own personal agendas. They are interested in only interpretations that support their interests of maintaining authority over others or the respect of others. They are interested in interpretations that allow them to gain the riches of authority--to continue to play 'god.' In other words, they use Jesus’ words to achieve their own self interests. Thus, the real meaning of Jesus' words pass right over them.
The later part of Jesus’ statement was drawn from the texts of Isaiah. Here is the context of Isaiah's statement:
Then I heard the voice of the Lord saying, Whom shall I send? And who will go for us? And I said, Here am I. Send me!
He said, “Go and tell this people: 'Be ever hearing, but never understanding; be ever seeing, but never perceiving.’ Make the heart of this people calloused; make their ears dull and close their eyes. Otherwise they might see with their eyes, hear with their ears, understand with their hearts, and turn and be healed.”
Then I said, For how long, O Lord? And he answered:
“Until the cities lie ruined and without inhabitant, until the houses are left deserted and the fields ruined and ravaged, until the LORD has sent everyone far away and the land is utterly forsaken.”
One might ask why God is telling His servant Isaiah to make the hearts of people in that society calloused. It is because of offensiveness. They did not want to hear from God. They had offended God and had offended God’s previous messengers. They had sent a clear message to God, from their actions and their lack of appreciation for God's previous messengers that they did not want to hear from Him. They wanted to continue to try to enjoy the world separately from Him.
On the other hand, whomever treats God’s servants with respect and humility—and appreciation for their teachings--they are offered the doorway into God’s world. Why? Because God’s world is bound by loving relationships.
For many in today’s Christian organizations, they will not hear or perceive Jesus’ teachings because they have become offensive towards Jesus. They have utilized Jesus' teachings and service for their own purposes. For many it may be as simple as gaining the acceptance of those around them. So they go to particular churches or join organizations in order to be accepted by a community of people. They hear the interpretations of offensive teachers who get paid to spread misinterpretations of what Jesus said, and they accept them because they do not want to be rejected by others in the assembly. They don’t want to be criticized for reading Jesus’ words directly and understanding them with humility, prayer and sincerity. Here again, the personal self interests of the person are overriding the hearing of the Truth, because of a desire to be respected and admired by others.
Those who are driven by humble curiosity to understand the true meaning of Jesus words: Those who do not care what others think, and who have a desire to know God as He is, ride through these challenges. For these people, God sees their sincerity, and gives them the understanding to be able to hear without an agenda. He gives them the internal vision to see the Truth that Jesus is presenting. For these people, Jesus’ words eventually gain clear meaning. For these people, the Truth is available, not because of some kind of position or title, and not because they are members of this organization or that organization. The Truth is available to a person simply because of their sincerity, their respect, their appreciation and their determination to learn about God.