Gnostic Light

The Metaphor (the Darkness)
The Darkness represents the initial result of sin. That of separation from reality which is "The All". Phrases have been build by God into society to help us understand this concept like: "Being lost your own little world", "Lost in Thought", "Snap out of it", "Pay Attention", "Come back to earth", "head in the clouds".

A Description of the Darkness

And He said, “Go, and tell this people: ‘Keep on hearing, but do not understand; Keep on seeing, but do not perceive.’ 10 “Make the heart of this people dull, And their ears heavy, And shut their eyes; Lest they see with their eyes, And hear with their ears, And understand with their heart, And return and be healed.” (Isaiah 6:9-10 NKJV)

Jesus teaches these Metaphors Light and Darkness

The lamp to the body is one's focus, if therefore your focus is of undivided attention and seeing clear, your body is full of light, 23 but if your focus is toilsome, all of your body will be full of darkness, then if that light within you is darkness, how great is that darkness. (Matthew 6:22-23)

Judgement has already been declared by Jesus

And this is the condemnation, that the light has come into the world, and men loved darkness rather than light, because their deeds were evil. 20 For everyone practicing evil hates the light and does not come to the light, lest his deeds should be exposed. 21 But he who does the truth comes to the light, that his deeds may be clearly seen, that they have been done in God.” (John 3:19-21 NKJV)

Important: I do not vouch for this NKJV translation, however it is good enough to explain that being in the light is God's will.

To single your focus on the now, Jesus taught it like this:

Jesus said to him, "If you want to be perfect, go, sell what you have and give to the poor, and you will have treasure in heaven; and come, follow Me." (Matthew 19:21 NKJV)

Possession minded people (as most are, and even the rich man in this story) think of selling everything they own, and automatically think of their objects that they own. However, the true possessions that you own are your thoughts that have been given to you by God.

“Do not lay up for yourselves treasures on earth, where moth and rust destroy and where thieves break in and steal; 20 but lay up for yourselves treasures in heaven, where neither moth nor rust destroys and where thieves do not break in and steal. 21 For where your treasure is, there your heart will be also. (Matthew 6:19-20 NKJV)

So by selling all of our thoughts and paying attention to the one speaking at us (the beggar), we gain seeds of truth into our memory (a treasure in heaven).

Explained in most of his parables, however he makes it easier for us to see this in two of his parables.

The Parable of the Sower
When reading the parable you learn of four states that a mind can be in. Three of the states represent the Darkness, and the one state represents the Light.

• The Wayside(The saying is not understood)
• The Thorny Place(The saying is crowded out by to many other thoughts)
• The Stoney Ground(This mind hates what it hears so does not retain in memory)

Finally

• The Good Ground(A mind willing to hear and understand)

The Parable of the Wheat and the Tares
When the person starts to talk to you, the temptation is to "pull the weeds" correct the incorrect saying. However we are instructed by the Master not to pull the weeds, and instead wait until we have heard the entire message from the beginning to the end. Then after we have heard the entire message, the forget the error, and to gather the good sayings into the memory.

Why the healing does not come
Because our focus is on so many projects when in the darkness. The mind must use many resources to continually be able to process all of these different activities. So the mind never gets to rest to allow the body to heal. It is like lifting weights over and over again. The body takes a very long time to heal, since it does not get its rest. Those that want the scientific explanation just ask. I'd rather someone ask for it, then to waste time writing it, when it is not cared about and thrown away by the ones that do not understand. Thanks.

As Paul Explains it

Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ; (2 Corinthians 10:5 KJV)

This Greek word that the scribe translates as imaginations is (λογισμοὺς) meaning: reasoning, thinking; a conception.

So thinking is our enemy, for the deeper we think, the further our focus fades from reality. So by casting away our own thoughts, and simply become aware. We see what is going on, and hear what is being said. This allows us to be baptized or born again into the breath of the speaker.

My mind brings to reference a scripture, however I fail at finding it, maybe the Light can give me remembrance. However the point to it is this. We will be judge by what is inside of us, and we will be judge by what is not inside of us. For if we heard, and do know what the sower has said, and can hold it in our hearts. Then we are free from a condemnation. However what I did not hear, so therefore is not inside of me. Because it is not inside of me. Then I do receive condemnation.

Therefore I encourage each of you to live the truth of this, and to be children of Light. For your sake, because I love you.

Here's a bit of perspective from the Gospel of John:

“Rabbi,” his disciples asked him, “why was this man born blind? Was it because of his own sins or his parents’ sins?”

“It was not because of his sins or his parents’ sins,” Jesus answered. “This happened so the power of God could be seen in him.

—John 9:2-3 NLT

So one reason someone might be kept broken would be so they could be healed later to show the power of God.

(Note: Not sure if this answers the question fully or not, because I'm not 100% sure what exactly you're asking. If it doesn't answer, please comment why so I can fix it)

"Those who have ears, ought to hear," was how Jesus would end his proclamations.

"He has sent me to bind up the brokenhearted, to proclaim freedom for the captives and release from darkness for the prisoners,"

Isaiah 61

Is was Jesus himself says about Himself in the Synagogue. Jesus would be the one who lifts the scales off our eyes by rubbing mud He made from His spit in them. And what does the fella see who has his eyes opened? People who kinda look like trees... Well, that may be what the people were, they are blind like he was blind, but their blindness is spiritual blindness that comes from within.

Spiritual blindness can only be cured by supernatural means. And spiritual means come in two packages, Actual and Sanctifying Grace. Actual Grace, being the grace to get up and do good works and Sanctifying Grace being the grace freely given by Jesus' sacrifice on the Cross.

And now, if you'll bear with me, I'll attempt to connect the dots in my brain and you can tell me if it makes sense not. Grace is the thing God gives us, our souls are what perceive it, if our souls are blind (like the tree people or the folks in Isaiah) then we cannot perceive it. If, on the other hand, we are made to perceive it (or rather forced to perceive it, because we are already made to perceive it) then God has done the thing he doesn't do. He takes away our freewill and thereby diminishes our innate capacity to love Him to the fullest (which Jesus says is the greatest commandment). It wouldn't be the greatest commandment if it were merely a command performed by a magician "look into my eyes, you must love God with all your heart, with all your soul etc.)" that wouldn't be freewill and it wouldn't be love, it wouldn't be sacrificial or grace filled or even good. So, for some, it is dangerous to make them come forcibly into the light of God's glory, according to Moses, most folks would die if they tried.

However, this is not to say that they're doomed or mud people or in any way permanently deficient, its just where you (you apostles) are meeting this person now, it is not in their best interest to cure their blindness when what they need to do is learn to see.

also worth noting, from the footnotes of the New American Bible

Isaiah’s words give evidence that he attempted in every way, through admonition, threat, and promise, to bring the people to conversion (cf. 1:18–20), so it is unlikely that this charge to “harden” is to be understood as Isaiah’s task; more probably it reflects the refusal of the people, more particularly the leaders, who were supposed to “see,” “hear,” and “understand,” a refusal which would then lead to a disastrous outcome

so, I don't really understand what that means, it could be that Isaiah and Jesus are just echoing the reality of the situation. As if to say, "this is actually how you are and I am very sorry for your children's sake".)))

I consider a biblical answer of a person whose heart God hardened. Pharaoh, in the time of Moses, was shown repeatedly hardening his own heart, until finally the Lord began to harden his heart to the point of supernatural stupidity. The Lord made an example out of a bad man, who had chosen and committed himself to his wicked rebellion against the Lord. So, as in the case of the man born blind, the Lord spiritually blinded the man and hardened his heart in order that His glory and justice be seen. Pharaoh was free at first, and used his freedom to harden his own heart. The Lord magnified his folly!

There is a saying I grew up with, and if memory serves it goes:

"Light received begets more light. Light rejected begets more darkness."

In other words, each human being is responsible to God for the amount of spiritual light he or she has received. To accept even a ray of the light of God's truth begets more light. It's as if God waits for the slightest movement of faith toward him, and with that movement he bestows even more light, and so on.

On the other hand, to refuse the light one has, which was certainly the case with many of the outwardly religious people with whom Jesus interacted, given that they had "Moses and the prophets," leads invariably to spiritual deafness and blindness. Yes, the sound of Jesus' words entered their brains through their physical ears via the eardrum, hammer, anvil, cochlea, and auditory nerve, but they weren't truly listening. Had they been truly listening they would have believed Jesus' message. Similarly, their retinas captured the image of the man Jesus, saw him speaking, witnessed his miracles, and watched as people were won over by his message, but those retinal images led simply to greater and greater blindness because of unbelief.

Today, in our supposed sophistication, we invoke irony to describe the phenomenon of how, on the one hand, those religious people who should have seen, heard, and then believed, did not. On the other hand, those people whom the religious world had written off would gravitate to and believe Jesus' message of good news, liberation from sin, recovery of their spiritual sight, and freedom from oppression (see Luke 4:18-19).

I am not saying that Isaiah and Jesus did not appreciate and understand the irony of people's reactions to their messages. Their seemingly ironic words were more revelatory of the spiritual phenomenon with which I started this answer:

"Light received begets more light. Light rejected begets more darkness."

One of the great "I am's" of Jesus was

"'I am the light of the world; he who follows Me will not walk in the darkness, but will have the Light of life'" (John 8:12 NASB).

And,

"'While I am in the world, I am the Light of the world'" (John 9:5 NASB).

Compare these two passages with the apostle John's words in his first letter:

"This is the message we have heard from Him and announce to you, that God is Light, and in Him there is no darkness at all" (1:5 NASB Updated).

God desires for us to walk in fellowship with him in the light. We do so when we walk in obedience to the light of his word and the witness of his light within our hearts. True, that fellowship is broken when we sin and choose to walk in darkness (John 1:6, 8-10), but with confession and repentance come forgiveness, cleansing, and a renewal of fellowship with God.

As for those who are not children of God through faith in Christ, their continued refusal to forsake their darkness and embrace God's light is an indication of what the apostle Paul called the suppression of the truth in unrighteousness (Romans 1:18). Choosing to ignore the God-given light implanted in them by "the God who is there,"

". . . they became futile in their speculations, and their foolish heart was darkened. Professing to be wise; they became fools" (Romans 1:21b-22).

Here again is an irony: In becoming professors of wisdom, unbelievers succeed only in becoming fools. Paul echoes this thought in 1 Corinthians, chapter 1:

"For it is written, 'I WILL DESTROY THE WISDOM OF THE WISE, AND THE CLEVERNESS OF THE CLEVER WILL I SET ASIDE.' Where is the wise man? Where is the scribe? Where is the debater of this age? Has not God made foolish the wisdom of the world? For since in the wisdom of God the world through its [version of] wisdom did not come to know God, God was well pleased through the foolishness of the message preached [i.e., the gospel of Jesus Christ] to save those who believe. For indeed Jews ask for signs and Greeks for wisdom; but we preach Christ crucified, to Jews a stumbling block and to Gentiles foolishness, but to those who are the called, both Jews and Greeks, Christ [is] the power of God and the wisdom of God. For the foolishness of God is wiser than men, and the weakness of God is stronger than men" (vv.19-25).

In conclusion, Jesus "hit the nail on the head" when he said,

"'And this is the judgment, that the light hath come to the world, and men did love the darkness rather than the light, for their works were evil; for every one who is doing wicked things hateth the light, and doth not come unto the light, that his works may not be detected; but he who is doing the truth doth come to the light, that his works may be manifested, that in God they are having been wrought'" (John 3:19-21 YLT).

What is meant by keeping people blind and deaf so as not to get healed?

Perhaps one way to approach this question is by starting off with this story:

God Will Save Me

A terrible storm came into a town and local officials sent out an emergency warning that the riverbanks would soon overflow and flood the nearby homes. They ordered everyone in the town to evacuate immediately.

A faithful Christian man heard the warning and decided to stay, saying to himself, “I will trust God and if I am in danger, then God will send a divine miracle to save me.” The neighbors came by his house and said to him, “We’re leaving and there is room for you in our car, please come with us!” But the man declined. “I have faith that God will save me.”

As the man stood on his porch watching the water rise up the steps, a man in a canoe paddled by and called to him, “Hurry and come into my canoe, the waters are rising quickly!” But the man again said, “No thanks, God will save me.”

The floodwaters rose higher pouring water into his living room and the man had to retreat to the second floor. A police motorboat came by and saw him at the window. “We will come up and rescue you!” they shouted. But the man refused, waving them off saying, “Use your time to save someone else! I have faith that God will save me!”

The flood waters rose higher and higher and the man had to climb up to his rooftop. A helicopter spotted him and dropped a rope ladder. A rescue officer came down the ladder and pleaded with the man, "Grab my hand and I will pull you up!" But the man STILL refused, folding his arms tightly to his body. “No thank you! God will save me!”

Shortly after, the house broke up and the floodwaters swept the man away and he drowned. When in Heaven, the man stood before God and asked, “I put all of my faith in You. Why didn’t You come and save me?”

And God said, “Son, I sent you a warning. I sent you a car. I sent you a canoe. I sent you a motorboat. I sent you a helicopter. What more were you looking for?”

Before I summarize, here is - and this is the authoritative section - what The Navarre Bible New Testament Compact Edition's explanatory note for Mark 4:12 says:

, so that ...: One might rephrase this: "So that the scripture might be fulfilled"; cf. Jn 18:32; 19:24, 28. It was not God's intention to prevent their understanding. Matthew avoids this difficulty by writing, "I speak to them in parables because seeing they do not see" (Mt 13:13).

And its note to 4:10-12 says:

The Kingdom of God is a mystery. If the Twelve and the other disciples know baout it and understand it (cf. Mt 13:51), they do so by God's gift (v. 11: cf. Mt 13:11). The disciples are distinguished from "those outside" - a reference which normally applied to the Gentiles but which here applies to Jews who chose not to appreciate the signs worked by Jesus (cf. Lk 12:41). Those signs fulfil the words of prophet Isaiah (Is 6:9-10). When, in v. 12, Jesus says "so that ...",we might at first sight find it disconcerting; our LORD is in fact using a wording often found in the Bible (cf. Ex 4:21; 7:3, 13, 22; etc.) which attributes to God the actions of men. It is a way of referring to the mystery of how God's grace and man's corporation combine in salvific actions. We also find that when people sincerely seek God, he "opens hearts to understand" his words (cf. Acts 16:14).

Concluding Summary

We may have all perhaps encountered one time or another, a child, a student, a worker, an athlete, etc., who insist and persist in "my way", and as ridiculously as it sounds, even when they have asked for help.

One explanation from the foregoing is that it is God who gives unmerited grace to a person. The person is to respond with humility and gratitude.

Their own pride and lack of correspondence to God's grace is the thing that "blinds them", and they are unable even to recognize the graces God continually sends them. What is plain to the humble is missed or confusing to them.

Some have explained this as God withholding his grace. This may be what scripture means when it says God resists the proud or God hardening the heart as was the case with Pharaoh. In contrast, Naaman was only healed after he humbled himself. Similarly Nin′eveh, the great city was converted, and one of the ten lepers the only one saved when all ten had been cleansed of their leprosy.

I intentionally did not answer this question , on the off chance that I may again be given reps that I did not earn.

To my understanding of Scriptures; man has a very limited knowledge as opposed an omniscient God.

Isaiah 55:8 and 9 "For My thoughts are not your thoughts, Nor are your ways My ways," says the LORD. "For as the heavens are higher than the earth, So are My ways higher than your ways, And My thoughts than your thoughts.

Mans knowledge is limited in that we are prone to believe that if it does not exist in the material world it does not exist, this restricted knowledge, prevents us from the knowledge of many things. Just one instance is we wonder if there is intelligent life elsewhere in the Universe, however; the Creator God knows, another is the human mind is incapable of comprehending either endless Space or eternity. The human mind automatically believes there has to be something that begins where Space leaves off, without consideration of the basic fact that something has to go on endlessy. Jesus himself gave us the limitation of the human mind in chapter 3 of the book of John.

John 3:12 and 13 If I have told you earthly things and you do not believe, how will you believe if I tell you heavenly things? No one has ascended to heaven but He who came down from heaven, that is, the Son of Man who is in heaven.

Just take for instance verse 13 where he says no one came down from heaven except him, who is in heaven. Thereby indicating that he was in two places at the same time.

How can Jesus be both in Heaven and on Earth simultaneously? The answer to that is that they are not separate places, but are one and the same.

Let’s look at that before you call me a blithering idiot. Using Space as an example:

We are quite aware that Space is there, but Earth is in Space, so we are in fact on Earth and in Space at the same time. So let's go back to the time before Creation, and consider what was there before the beginning.

Before creation there was only God, and one of Gods characteristics which we humans are incapable of understanding is that God is Spirit. God being a spirit is unbound, by that I mean that God is just as Space without a starting place or an ending place, he also is unbounded in that he has no beginning and no end. The human mind is incapable of grasping that concept, and because we are bound by our human brain we; whether consciously or unconsciously; ascribe a beginning and an end to everything.

So let's take a part of the parable to which the question was asked, and see how we can use what I have said above to help us understand Luke chapter 8 verses 10.

Matthew 13:19 When anyone hears the word of the kingdom, and does not understand it, then the wicked one comes and snatches away what was sown in his heart. This is he who received seed by the wayside.

In the above example what Jesus is actually saying is, that when someone hears something about life beyond physical existence, and being present with God in spirit; but because of the limitations of the human mind; does not comprehend that the spiritual is eternal, and being eternal can go on and will go on without end. He goes on to say that Satan then comes in and uses the same trick that he always does and cast doubt in the mind of the hearer. And finally Jesus is saying that that person because of not understanding the eternal things, and did not put down roots which would have given him enough basic knowledge to understand the gospel. That left him in a position that the worries of the world overcame the desire for salvation.

So let's take that and see how it fits into Luke chapter 8 and verse 10.

Luke 8:10 And He said, "To you it has been given to know the mysteries of the kingdom of God, but to the rest it is given in parables, that 'SEEING THEY MAY NOT SEE, AND HEARING THEY MAY NOT UNDERSTAND.'

In this Scripture Jesus is telling the apostles that they have been given special knowledge so that that they can understand spiritual things such as being unbound, and the true meaning of both endless and eternal. He then goes on to say that what he does with the general public is to put things in simple terms which they can comprehend. They see the material world around them and they hear what he is saying, but they are unable to take those things outside of the physical world.

This narrow sightedness is just as prevalent today as it was in Jesus day. And all three of the instances in Jesus parable we find constantly happening today.

And to my narrow mind, it seems that because of that human limitation, Jesus chose to come to Earth and suffer the cross to save those seeds which fell on good ground.

Many answers are on the right track.

What is meant by keeping people blind and deaf so as not to get healed?

Many who went to hear Jesus were not there to hear the truth. Instead they were there to try to catch Jesus speaking against the law or commit blasphemy so as to find cause to condemn Him.

Therefore, Jesus directed this saying to all those who did not treasure the truth, nor come with an open heart for the Holy Spirit to work repentance. Heavenly pearls are not to be given to them to understand least they be healed, because they do not want to be healed and have insulted the Spirit of God.

For the same reason Jesus also said:

“Do not give what is holy to the dogs; nor cast your pearls before swine, lest they trample them under their feet, and turn and tear you in pieces." (Matthew 7:6)

Comparison with Matthew 13

For those who believe in the inerrancy of the Bible, further understanding of Mark 4:10-13 and Isaiah 6:9-10 can be found by comparing the passages with Matthew 13:13-15.

Here the same conversation is recorded, but with greater detail. Wording makes it clear that, though God permitted it, these people cannot see because they closed their own eyes.

(Matthew 13:15 NKJV) For the hearts of this people have grown dull. Their ears are hard of hearing, And their eyes they have closed, Lest they should see with their eyes and hear with their ears, Lest they should understand with their hearts and turn, So that I should heal them.’

The NIV translation also agrees:

(Matthew 13:15 NIV) For this people's heart has become calloused; they hardly hear with their ears, and they have closed their eyes. Otherwise they might see with their eyes, hear with their ears, understand with their hearts and turn, and I would heal them.'

Reliance on God

Therefore, for those of us who allow the prompting of the Holy Spirit to work change in us, the Holy Spirit gives us the spiritual discernment necessary to understand all parables. God leaves difficult passages and parables in the Bible so as to awaken our desire to understand and so we would rely only on Him for understanding. Spiritual things can only be spiritually discerned (1 Corinthians 2:14).

Since Jesus' advent, our understanding of the plan of salvation is much greater, and we are now living in a time where we have more light than the prophets of old:

(Mathew 13:17) For assuredly, I say to you that many prophets and righteous men desired to see what you see, and did not see it, and to hear what you hear, and did not hear it.

If we do not understand, we must ask God:

"If any of you lacks wisdom, let him ask of God, who gives to all liberally and without reproach, and it will be given to him." (James 1:5)

If we cannot see, we must repent and buy eye salve from God:

"I counsel you to buy from Me gold refined in the fire, that you may be rich; and white garments, that you may be clothed, that the shame of your nakedness may not be revealed; and anoint your eyes with eye salve, that you may see." (Revelation 3:18)

Those who have opportunity and access to the light must seek for further understanding, otherwise they would be guilty of being willfully blind.

ShemSeger's answer is the best, and very good. However, it needs to be placed in a comprehensive context of what God has made explicitly clear regarding the opening or closing of minds.

Scripture points out God wants everyone saved,

"who desires all men to be saved and to come to the knowledge of the truth" 2 Tim 2:3

but, at the same time Christ points out

"No one can come to me unless the Father who sent me draws them" John 6:44

Biblically, we first see this in practice when God cuts mankind off from Him and eternal life:

"Then the LORD God said, “Behold, the man has become like one of Us, knowing good and evil; and now, he might stretch out his hand, and take also from the tree of life, and eat, and live forever”— therefore the LORD God sent him out from the garden of Eden, ... So He drove the man out; and at the east of the garden of Eden He stationed the cherubim and the flaming sword which turned every direction to guard the way to the tree of life" Gen 3:22-24

Like ShemSeger's (good) answer, accountability is involved. And, that leads to judgement - with eternal consequences. But, it also points out to mercy ... as God states:

"Mercy triumphs over judgment" Jas 2:13

ALL of God's judgments are on a foundation of mercy. Including closing minds spiritually. But, as scripture points out, if you take the full context of the topic of opening and closing minds, they won't all remain closed.

To see that, you have to follow through the entire Bible with the idea of God choosing, or not choosing, with whom He is going to work with in a given time...

Summarizing this point in scripture:

• up until Ancient Israel and the Old Covenant, God dealt with a single human lineage. Although descended from this lineage, for the first time God is dealing with an entire nation - and no other nation ("He has done this for no other nation; they do not know his laws" Ps 147:20)

• until Pentecost, the Holy Spirit is not even available en masse to mankind. As the Lev 23 Holy Days point out TO THE VERY DAY, that'd be Pentecost when it finally is available (but, like most prophecy is hardly understood until after it passes).

• today, experience, history and scripture show most of mankind doesn't even respond to the Gospel, a very poor campaign for a Sovereign God if His will is for all men to be saved (2 Tim 2:3).

That last point is often refuted with the choice is in man's hands. But, you have to take that in context: God enables or disables someone to even be CAPABLE of making that choice. ... until an appointed time. This is explicit in scripture.

An example of this is given in Romans, where the Jews are deliberately blinded spiritually, but will not be so, by God's hands, at some appointed time in the future:

"For I do not want you, brethren, to be uninformed of this mystery—so that you will not be wise in your own estimation—that a partial hardening has happened to Israel until the fullness of the Gentiles has come in" Rom 11:25

This same theme is throughout scripture, God closing a mind or opening it, choosing a person or not choosing a person:

• Abraham chosen over the rest of mankind
• Israel over Ishmael
• Jacob over Esau
• Ephraim over Manasseh
• Judah over Reuben, Simeon and Levi (to be the Sceptar (ruler), Gen 49:10)
• Joseph over all his brothers (to have the birthright, 1 Chron 5:2), which birthright was doubled in his sons, Ephraim and Manasseh NOTE: correlate this to Isa 61:7, and there are other verses
• Ephraim over Manasseh

...

Then, there's the Old Covenant. That's clearly a national failure in documentation. And, scripture explains why, Hebrews is a good summary of why. In short, a law can't make one Holy in character, not can it forgive sins - for good. Holy character has to come from the heart. And, the only way that is possible is through the Holy Spirit. (Jer 31:31-33, Heb 8:8-10, Rom 8 contrasts the two covenants, and many, many more. The point: it was not the appointed time for Ancient Israel to be able to obey, receive and be saved...much less all the other nations on earth at the time who God has explicitly stated He wants to save. He isn't even dealing with them throughout this time!)

Then, you get to the New Covenant via Christ making the Holy Spirit available TO THE DAY on Pentecost (Lev 23:15-17, and note "firstfruits" in v17).

Then, look at Christ's ministry where it was not given to some to understand the parables. This practice has already been going on throughout scripture. Understanding that is critical to understanding the context of Christ's ministry not being available to all those people - at that time. And, the fact they will have an appointed time. (That is pointed out in another answer, in the context they may join the church later. In contrast, they won't be doing so IN THIS AGE, many of them anyway).

2 Tim 2:3 is God's goal, it would be very wise of believers to expect God is going to do far better than saving the souls we see coming to Christ now. And, scripture continues this theme timeline into the future, explicitly, to support that expectation.

Some highlights are the discussion in Romans 9-11 where, explicitly this entire topic is expanded in detail like few other places in scripture (other than Isaiah and Ezekiel do indeed document post-Second Coming resurrection and life, e.g. Isa 65-66).

Inside this Romans discussion is the specific-purpose statement for this entire theme:

"For the Scripture says to Pharaoh, “FOR THIS VERY PURPOSE I RAISED YOU UP, TO DEMONSTRATE MY POWER IN YOU, AND THAT MY NAME MIGHT BE PROCLAIMED THROUGHOUT THE WHOLE EARTH.” Romans 9:17

God's purpose for opening or closing a mind to spiritual truth is FOR ALL MANKIND. (It's very short-sighted, and contradicts scripture, to think that meant in Pharoah's time. No, it is for all mankind, keeping mind what has yet to happen with all mankind ... Ez 37, Rev 20:5, 13, ... and scripture is sprinkled with things like this: Deut 4:19 "All nations", yet God hasn't worked with all nations...yet).

...which brings us to the age to come, the millenium and then post-millenium. Both are explicit in scripture.

• Christ rules 1,000 years on the earth Rev 5:10

• ALL THAT LIVED will be resurrected, in a second resurrection: Rev 20:5

Then, you can point back to some post Second Coming major prophets discussion on what life will be like then. One very important point: the Second Coming is NOT a condemnation of all those in it. The judgement of that time will be an opportunity to THEN have their minds open (John 6:44), because it is explicitly clear (and sufficiently pointed about above) God has deliberately closed the majority of minds in this age. Yet, has made His will explicit, too: He wants them **all* to come to eternal life.

Bet on it: He will do just that (barring the Heb 6:6 category, but NO ONE dying in this age not having received Christ is condemned, they CAN'T be without rejecting Christ. Failing to receive Him is only two categories: Heb 6:6 and those who've never responded. The latter are being reserved for a future time when Almighty God deems it most wise to open their minds.

"There is a time for everything, and a season for every activity under the heavens" Ecc 3:1

TL; DR: This was a necessary out-working of God's plan to see the ingathering of the Gentiles (to be included in the family of God).

A key part of scripture that gives us insight into this question is found in Romans chs 9-11 which summarizes:

• How God exercises his soveriegn choice in calling to himself a people of faith, and how this includes not just (a remnant of) Israel (the Jews), but Gentiles as well (cf. Romans 9:1-29). Key verses:

...18 Therefore God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden. ...

...22 What if God, although choosing to show his wrath and make his power known, bore with great patience the objects of his wrath—prepared for destruction? 23 What if he did this to make the riches of his glory known to the objects of his mercy, whom he prepared in advance for glory— 24 even us, whom he also called, not only from the Jews but also from the Gentiles? 25 As he says in Hosea:

“I will call them ‘my people’ who are not my people; and I will call her ‘my loved one’ who is not my loved one,”

26 and,

“In the very place where it was said to them, ‘You are not my people,’ there they will be called ‘children of the living God.’” ...

• How Israel (the generality of the Jews) lapsed into spiritual blindness and unbelief (cf. Romans 9:30-10:21), but salvation is given to (all) those who believe the gospel. Key verses:

... 31 but the people of Israel, who pursued the law as the way of righteousness, have not attained their goal. 32 Why not? Because they pursued it not by faith but as if it were by works. They stumbled over the stumbling stone. 33 As it is written:

“See, I lay in Zion a stone that causes people to stumble and a rock that makes them fall, and the one who believes in him will never be put to shame.”

10 Brothers and sisters, my heart’s desire and prayer to God for the Israelites is that they may be saved. 2 For I can testify about them that they are zealous for God, but their zeal is not based on knowledge. 3 Since they did not know the righteousness of God and sought to establish their own, they did not submit to God’s righteousness. 4 Christ is the culmination of the law so that there may be righteousness for everyone who believes. ...

... 11 As Scripture says, “Anyone who believes in him will never be put to shame.” 12 For there is no difference between Jew and Gentile—the same Lord is Lord of all and richly blesses all who call on him, 13 for, “Everyone who calls on the name of the Lord will be saved.” ...

• How God has preserved for himself a faithful remnant amongst Israel (cf. Romans 11:1-10). Key verses:

... 2 God did not reject his people, whom he foreknew. Don’t you know what Scripture says in the passage about Elijah—how he appealed to God against Israel: 3 “Lord, they have killed your prophets and torn down your altars; I am the only one left, and they are trying to kill me”? 4 And what was God’s answer to him? “I have reserved for myself seven thousand who have not bowed the knee to Baal.” 5 So too, at the present time there is a remnant chosen by grace. ... [Emphasis added]

... 7 What then? What the people of Israel sought so earnestly they did not obtain. The elect among them did, but the others were hardened, 8 as it is written:

“God gave them a spirit of stupor, eyes that could not see and ears that could not hear, to this very day.” ... [note the similarity between this quote and that in the OP - this first part from a different portion of Isaiah (29:10), the latter part is a reference to the very same passage quoted in Mark (Isaiah 6:9-10)]

• The Gentiles who have responded (or will respond) in faith have been 'grafted' in to God's people. This serves to 'provoke' Israel to jealousy for the Lord and return to Him. (cf. Romans 11:11-36). Key verses:

11 Again I ask: Did they stumble so as to fall beyond recovery? Not at all! Rather, because of their transgression, salvation has come to the Gentiles to make Israel envious. ... [Emphasis added]

... 17 If some of the branches have been broken off, and you [ie Gentiles], though a wild olive shoot, have been grafted in among the others and now share in the nourishing sap from the olive root, 18 do not consider yourself to be superior to those other branches. If you do, consider this: You do not support the root, but the root supports you. 19 You will say then, “Branches were broken off so that I could be grafted in.” 20 Granted. But they were broken off because of unbelief, and you stand by faith. Do not be arrogant, but tremble. 21 For if God did not spare the natural branches, he will not spare you either. ...

... 25 I do not want you to be ignorant of this mystery, brothers and sisters, so that you may not be conceited: Israel has experienced a hardening in part until the full number of the Gentiles has come in, 26 and in this way all Israel will be saved. As it is written:

“The deliverer will come from Zion; he will turn godlessness away from Jacob. 27 And this is my covenant with them when I take away their sins.”

28 As far as the gospel is concerned, they are enemies for your sake; but as far as election is concerned, they are loved on account of the patriarchs, 29 for God’s gifts and his call are irrevocable. ... [Emphasis added]

Summary: God never stopped loving Israel, but he allowed their hearts to harden (by with-holding his grace to prevent this) in order that the Gentiles could enter the kingdom. This is a temporary condition until 'the full number of the Gentiles has come in' at which point: The veil will be taken away and they will look on him whom they have pierced and mourn (cf. Zechariah 12:10); and then all Israel turn to the Lord through faith in their revealed Messiah. (In the mean-time, God has preserved in his grace a remnant from Israel).

TL;DR: Milk before meat. Deep doctrine is dangerous to an unprepared soul.

"I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able." (see 1 Corinthians 3:1-3)

Christ taught in parables [as did Isaiah] so that the spiritually immature and spiritually mature could both benefit from the message. He kept the deeper doctrines hidden in the parable from those who were spiritually "blind" and "deaf" to them until they matured spiritually enough that they could bear the deeper doctrines, and be healed by them.

Understanding Isaiah

You are right that this is one of those scriptures that is meant to challenge our understanding. Prophets like Isaiah veiled their teachings in language that preserved their teachings for those who would understand with their heart. Isaiah’s words are similar to the parables of Jesus in their manner of teaching. Spiritually speaking, Isaiah’s writings are meat, not milk (see 1 Corinthians 3:1–3; Hebrews 5:13–14; Isaiah 28:9). It requires spiritual maturity to understand them.

Prophecy of the Rejection of Spiritual Things

Isaiah 6 is a prophecy of the Jews rejecting Christ's teachings. The words the prophet Isaiah was commissioned to deliver were in part to bring the people to a full accountability for their choices, so that they would be left without excuse. The words are better understood:

"And he said: Go and tell this people—Hear ye indeed, but [they] understood not; and see ye indeed, but [they] perceived not."

The people claimed to hear and see, but they did not understand the spirit of the message.

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UPDATE – in response to OP edit:}

"Make the heart of this people fat, and make their ears heavy, and shut their eyes; lest they see with their eyes, and hear with their ears, and understand with their heart, and convert, and be healed." (Isaiah 6:10)

Keil and Delitzsch, Commentary on Isaiah 6:

The command to “make the heart of this people fat, … their ears heavy, and shut their eyes” is used to describe the process of making the people accountable. The command, of course, refers to “their spiritual sight, spiritual hearing, and spiritual feeling.” (Keil and Delitzsch, Commentary, 7:1:200).

“There is a self-hardening in evil. … Sin from its very nature bears its own punishment. … An evil act in itself is the result of self-determination proceeding from a man’s own will.” (Keil and Delitzsch, Commentary, 7:1:201).

An individual cannot resist or reject the truth without eventually becoming spiritually hardened.

Isaiah’s indictment of the kingdom of Judah was cited again in the New Testament to show that the people of that time were no different. The inability of many to understand the parables is a fulfillment of Isaiah’s prophecy:

"And his disciples asked him, saying, What might this parable be? And he said, Unto you it is given to know the mysteries of the kingdom of God: but to others in parables; that seeing they might not see, and hearing they might not understand." (see Luke 8:9–10; also see Matthew 13:10–17).

The significance of many of the miracles was also misunderstood:

"He hath blinded their eyes, and hardened their heart; that they should not see with their eyes, nor understand with their heart, and be converted, and I should heal them." (see John 12:37–41).

The testimony of the Messiah and His Sonship was understood, at least in part, by the disciples, but it was rejected by others:

"21 ¶In that hour Jesus rejoiced in spirit, and said, I thank thee, O Father, Lord of heaven and earth, that thou hast hid these things from the wise and prudent, and hast revealed them unto babes: even so, Father; for so it seemed good in thy sight.

22 All things are delivered to me of my Father: and no man knoweth who the Son is, but the Father; and who the Father is, but the Son, and he to whom the Son will reveal him.

23 ¶And he turned him unto his disciples, and said privately, Blessed are the eyes which see the things that ye see:

24 For I tell you, that many prophets and kings have desired to see those things which ye see, and have not seen them; and to hear those things which ye hear, and have not heard them." (see Luke 10:21–24).

In direct response to your comment:

"... it is mentioned that people should be deaf and blind until the cities crash down and the human population is decimated."

"Then said I, Lord, how long? And he answered, Until the cities be wasted without inhabitant, and the houses without man, and the land be utterly desolate," (Isaiah 6:11).

The prophet Isaiah asked the Lord how long some men would be hardened against truth (v. 11); the answer—until mortal man no longer exists.

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Understanding Parables

These scriptures refer to spiritual understanding. Many of the people of Jesus’ time were spiritually immature and unprepared to receive the doctrines He taught (they have eyes, but they can't "see" the deeper meaning). Through parables He was able to teach the more spiritually mature and at the same time veil His teachings from those who were not prepared to understand or follow them. In that manner He kept many from being condemned for having a knowledge of principles they were unable to live.

"That seeing they may see, and not perceive; and hearing they may hear, and not understand [hear the message, but not understand the deeper spiritual context]; lest at any time they should be converted, and their sins should be forgiven them [so that they can can join the church later, without being held accountable for sinning while having a greater understanding of spiritual things]." (Mark 4:12; KJV)

Matthew's account gives us more clarity on his words:

11 He answered and said unto them, Because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given...

13 Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand...

15 For this people’s heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes, and hear with their ears, and should understand with their heart, and should be converted, and I should heal them.

16 But blessed are your eyes, for they see: and your ears, for they hear. (Matthew 13:11,13,15-16)

In answer to your question, the people cannot be healed until their spiritual eyes are opened, and they can hear with their spiritual ears. Only then can they understand with their heart. Therefore it is prudent to keep them blind and deaf to the deeper "meatier" doctrines until they are spiritually mature enough to "stomach" them, Otherwise it could be detrimental to their spiritual development, much like giving meat instead of milk to a suckling babe would be detrimental to the physical health of the baby.

The Savior’s parables therefore included an implied invitation to seek further understanding of the truths they contained, and those who did so were rewarded with greater enlightenment.

A simple illustration showing why some people may fail to understand the truths taught in parables:

“Two men may hear the same words; one of them listens in indolence and indifference, the other with active mind intent on learning all that the words can possibly convey; and, having heard, the diligent man goes straightway to do the things commended to him, while the careless one neglects and forgets. The one is wise, the other foolish; the one has heard to his eternal profit, the other to his everlasting condemnation” (Jesus the Christ, 3rd ed. [1916], 297).

^{The Establishment of Zion (Isaiah 1–12), (13-37). Old Testament Student Manual Kings-Malachi, (1982), 137–50.
Understanding Isaiah, (E-3) Old Testament Student Manual Kings-Malachi, (1982), 131–35.
Chapter 5: Matthew 13–15, Matthew 13:13. “They Seeing See Not” New Testament Student Manual, 2014.}