Why did Jesus use parables to teach?

The spiritual eyes and ears of the Jewish leaders were closed during the earthly ministry of Jesus. He was standing at the door of their heart, knocking for them to open the door and let him in. He wasn't going to kick it down and force his way in, they had to open it themselves. The words Jesus spoke were spiritual and could be perceived by the human mind using spiritual senses not physical. see Rev.3:20, John 6:63

One idea that is almost never indulged is that perhaps Christ did NOT speak in parables, but according to his own experience. The synoptic gospels present a gap in the life of Joshua (Jesus to most) from the ages of 12 and 30. There are so many possibilities here that it is hard to talk about! But, I don't see why he could not have traveled (perhaps with his uncle, Joseph of Arimathea, in who's tomb he was buried) and experienced these things first hand...

Being brought up in a Protestant, Evangelical church, I found myself in Sunday school from age six. I remember one of my teachers, Mrs. Valcore, telling me that a parable is an "earthly story with a heavenly meaning." That's a decent definition, to be sure, but there's more to it than that.

Skip forward about 50 years, and in a Sunday school class for adults I learned that the purpose of a parable is to get the listener to lay his life alongside the parable in order for him or her to find its application. In other words,

• here is the story

• here is my life

• here is what the story is saying about my life

• In light of what it's saying, how is its message relevant to me, if at all? Is there anything I should now do, or say, or feel differently about. If so, how?

In perhaps Jesus' most powerful parable, the story of the "Prodigal Son," Jesus had two audiences. His first audience comprised people who in searching the story for a parallel to their lives identified with the younger son who demanded his inheritance, left home, and then wasted his money in short order, only to be in such want that he had to return home to ask his father for forgiveness.

The other audience comprised people who probably didn't identify with either son. If they identified with anyone in the story, it was likely the father because he appears to have been cursed with a wayward and ungrateful son. Toward the father they may have felt compassion.

Jesus' purpose for the latter audience, however, was to get them to identify with the elder son because he kept his nose clean, worked hard, respected his father, and had only contempt for--and possibly some envy of--his younger brother for having his cake and eating it too, as it were.

Quite likely the majority of the latter audience, composed as it was of hyper-vigilant Pharisees and scribes (see Luke 15:1-2), wouldn't identify with the older son in the way Jesus wanted them to identify with him until after they had mulled the story over in their minds for awhile.

Eventually, some of them (a remnant? a minority?) would be convicted of having the same holier-than-thou attitude of the older son and might just repent of their self-righteousness. For some others of them, Jesus' point would have sailed right over their heads, and their identification with the older son would have stopped with the notion that the older son was righteous before God and had no need to repent of anything.

Now perhaps you can understand why Jesus spoke in parables. Upon hearing Jesus' story of the two sons and their father, only those listeners who recognized their need to repent, as did the younger son, would be welcomed back into the bosom of the heavenly Father. Those listeners who failed, as did the older son, to recognize their need to repent would be at odds with the heavenly Father until they confessed their sin of self-righteousness to him.

Jesus knew that God's word as it came from his lips to his listeners ears would not return unto God void or empty (see Isaiah 55:11). For some of Jesus' listeners the return would be immediate in the form of a changed life, though some would fall away for various reasons (see Jesus' parable of the sower in Matthew Chapter 13).

For others of Jesus' listeners, the return might come much later or perhaps not at all. For either category of listeners, however, God's word would accomplish its purpose, whether that purpose was to grant repentance to a sinner or to confirm a sinner in his sin.

Such is the power of God's word, whether it is presented in a discursive manner or whether it is packaged in story form. Jesus was a master teacher in both modes. Moreover, his teaching, when believed, brought life; when not believed, death. And so it is with faithful Christian witness, preaching, and teaching today (see 2 Corinthians 2:14-17).

James E. Talmage discusses this in his book "Jesus the Christ" (read online here)

An excerpt from this chapter:

To the chosen and devoted followers who came asking the Master why He had changed from direct exposition to parables, He explained that while it was their privilege to receive and understand the deeper truths of the gospel, “the mysteries of the kingdom of heaven” as He expressed it, with people in general, who were unreceptive and unprepared, such fulness of understanding was impossible. To the disciples who had already gladly accepted the first principles of the gospel of Christ, more should be given; while from those who had rejected the proffered boon, even what they had theretofore possessed should be taken away. “Therefore,” said He, “speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.”

...

There is plainly shown an element of mercy in the parabolic mode of instruction adopted by our Lord under the conditions prevailing at the time. Had He always taught in explicit declaration, such as required no interpretation, many among His hearers would have come under condemnation, inasmuch as they were too weak in faith and unprepared in heart to break the bonds of traditionalism and the prejudice engendered by sin, so as to accept and obey the saving word.

Another example of the merciful adaptation of the word of truth to the varied capacities of the people who heard the parables is found in the psychological fact, that the incidents of an impressive though simple story will live, even in minds which for the time being are incapable of comprehending any meaning beyond that of the common-place story itself. … And then, when time and experience, including suffering perhaps, had prepared them for deeper thought, they would find the living kernel of gospel truth within the husk of the simple tale.

(Talmage)

In short, listeners of varying spiritual maturity could be taught that which they needed to hear.