‘You will keep on hearing, but will not understand;But blessed are your eyes, because they see; and your ears, because they hear.
You will keep on seeing, but will not perceive;
For the heart of this people has become dull,
With their ears they scarcely hear,
And they have closed their eyes,
Otherwise they would see with their eyes,
Hear with their ears,
And understand with their heart and return,
And I would heal them.’
Matthew 13:10-16 NASB
par·a·ble [par-uh-buhl]: a short allegorical story designed to illustrate or teach some truth, religious principle, or moral lesson.
Origin: 1275–1325; Middle English parabil < Late Latin parabola comparison, parable, word < Greek parabolḗ comparison, equivalent to para- side by side + bolḗ a throwing
Synonyms: allegory, homily, apologue.
Based on the Random House Dictionary, © Random House, Inc. 2013.
When Jesus explained to his disciples the reason he taught in parables, he was not giving them instructions to follow in order to achieve effective pedagogy. Just the opposite, in fact: parables, as used by Jesus, were meant to be equivocal in order to give an out to those not willing to learn. Some would consider that deceptive, I consider that brilliant, and far more to the point--effective to the purpose Jesus was aiming to achieve.
For those with the faith perspective God desires, it's divine message is all too clear. For those without that perspective, they see no divine message at all. Someone might protest that that is deceptive. If it is (and I don't think that is the case), it is no more deceptive than Jesus teaching by parables. God knows what makes for everlasting life and is well within his rights to filter for that amongst the creatures he's made in his image. The problem involved is with the hearers and seers, not with the communicator.
And let's be clear here: this phenomenon is not a mere accident, the foibles of communication, nor simply a trick. There is an "otherwise" at play in this that the unhearing consciously act according to. There are consequences to seeing or hearing with a faith perspective, repercussions that are just too repulsive to abide in their judgment. So they close their eyes, and stop their ears, and guard their hearts against the parable of creation.