The Holy Spirit
Humans are intelligent creatures. We can think, we can reason, we can form opinions. But physical humans are flesh. Our minds are naturally carnal. Human reasoning is self-serving. No matter how hard we may try, no matter how hard we may think that we may want to try, we cannot understand the Spiritual Truth of God without The Holy Spirit of God. It's the key that unlocks the Scriptures.
The Holy Spirit makes it possible for us to "hear" what God is actually saying. Without it, we may read the Bible, and become great "experts" of the Bible, and still not really understand what it says. And, as amazing as it may seem, that's exactly how God wants it.
Salvation In Stages
The Bible speaks of two separate and widely-spaced resurrections, the first at The Return Of Jesus Christ (1 Thessalonians 4:16-17), and the second 1,000 years later (Revelation 20:5). Those in the first resurrection will reign with Jesus Christ during the "millennium" (Revelation 20:6). They will not face a judgment after their resurrection, otherwise they would not be resurrected as immortal spirit beings. Those who awaken then will have made it. They are being judged now, or have been judged in whatever time that they lived during the past.
Those awakened after the 1,000 years will be resurrected physical (e.g. Ezekiel 37:1-14), and will later face a judgment, based on what they do with the knowledge that they will have then. Those who obey will be granted eternal life, those who refuse to obey will be cast into the lake of fire. Those resurrected later will absolutely not be getting a second chance, but their first chance, later. There are no "second" chances.
Few Truly With "Ears" Now
The Lord gives the "ears to hear":
"These are the words of the covenant which The Lord [see Rock Of Ages] commanded Moses to make with the people of Israel in the land of Moab, besides the covenant which He had made with them at Horeb. And Moses summoned all Israel and said to them: "You have seen all that The Lord did before your eyes in the land of Egypt, to Pharaoh and to all his servants and to all his land, the great trials which your eyes saw, the signs, and those great wonders; but to this day The Lord has not given you a mind to understand, or eyes to see, or ears to hear." (Deuteronomy 29:1-4 RSV)
"Thou Hast Hidden These Things":
"At that time Jesus declared, "I thank Thee, Father [see The Father and The Logos], Lord of heaven and earth, that Thou hast hidden these things from the wise and understanding and revealed them to babes; yea, Father, for such was Thy gracious will. All things have been delivered to Me by My Father; and no one knows the Son except The Father, and no one knows The Father except the Son and any one to whom the Son chooses to reveal Him." (Matthew 11:25-27 RSV)
Why Jesus used parables:
"He who has ears, let him hear." Then the disciples came and said to Him, "Why do you speak to them in parables?" And He answered them, "To you it has been given to know the secrets of the kingdom of heaven, but to them it has not been given" (Matthew 13:9-11 RSV) (see Why Parables?)
Even the apostles didn't understand at first:
"Then He said to them, "These are My words which I spoke to you, while I was still with you, that everything written about Me in the law of Moses and the prophets and the psalms must be fulfilled." Then He opened their minds to understand the Scriptures" (Luke 24:44-45 RSV)
A Later Time When All Will Have "Ears"
A physical resurrection:
"The hand of The Lord was upon me, and He brought me out by the Spirit of The Lord, and set me down in the midst of the valley; it was full of bones. And He led me round among them; and behold, there were very many upon the valley; and lo, they were very dry. And He said to me, "Son of man, can these bones live?" And I answered, "O Lord God, Thou knowe."
"Again He said to me, "Prophesy to these bones, and say to them, O dry bones, hear the word of The Lord. Thus says The Lord GOD to these bones: Behold, I will cause breath to enter you, and you shall live. And I will lay sinews upon you, and will cause flesh to come upon you, and cover you with skin, and put breath in you, and you shall live; and you shall know that I am The Lord."
"So I prophesied as I was commanded; and as I prophesied, there was a noise, and behold, a rattling; and the bones came together, bone to its bone. And as I looked, there were sinews on them, and flesh had come upon them, and skin had covered them; but there was no breath in them."
"Then He said to me, "Prophesy to the breath, prophesy, son of man, and say to the breath, Thus says The Lord God: Come from the four winds, O breath, and breathe upon these slain, that they may live." So I prophesied as He commanded me, and the breath came into them, and they lived, and stood upon their feet, an exceedingly great host."
"Then He said to me, "Son of man, these bones are the whole house of Israel. Behold, they say, 'Our bones are dried up, and our hope is lost; we are clean cut off.' Therefore prophesy, and say to them, Thus says The Lord God: Behold, I will open your graves, and raise you from your graves [see What Happens When You Die?], O My people; and I will bring you home into the land of Israel. And you shall know that I am The Lord, when I open your graves, and raise you from your graves, O My people. And I will put My Spirit within you, and you shall live, and I will place you in your own land; then you shall know that I, The Lord, have spoken, and I have done it, says The Lord." (Ezekiel 37:1-14 RSV)
Teachers hidden no more:
"And though The Lord give you the bread of adversity and the water of affliction, yet your Teacher will not hide himself any more, but your eyes shall see your Teacher. And your ears shall hear a word behind you, saying, "This is the way, walk in it," when you turn to the right or when you turn to the left. Then you will defile your silver-covered graven images and your gold-plated molten images [see Images and Idols]. You will scatter them as unclean things; you will say to them, "Begone!"
"And He will give rain for the seed with which you sow the ground, and grain, the produce of the ground, which will be rich and plenteous. In that day your cattle will graze in large pastures; and the oxen and the asses that till the ground will eat salted provender, which has been winnowed with shovel and fork. And upon every lofty mountain and every high hill there will be brooks running with water, in the day of the great slaughter, when the towers fall. Moreover the light of the moon will be as the light of the sun, and the light of the sun will be sevenfold, as the light of seven days, in the day when The Lord binds up the hurt of His people, and heals the wounds inflicted by His blow." (Isaiah 30:20-26 RSV)
No "Second" Chances
There are no "second chances" for those who have had the opportunity to truly understand. Once the Truth is known, whether sooner or later, a choice must be made to repent and live, or rebel and burn. There is only one chance:
"For if, after they have escaped the defilements of the world through the knowledge of our Lord and Savior Jesus Christ, they are again entangled in them and overpowered, the last state has become worse for them than the first. For it would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them." (2 Peter 2:20-21 RSV)
"For it is impossible to restore again to repentance those who have once been enlightened, who have tasted the heavenly gift, and have become partakers of the Holy Spirit, and have tasted the goodness of The Word of God and the powers of the age to come, if they then commit apostasy, since they crucify the Son of God on their own account and hold Him up to contempt. For land which has drunk the rain that often falls upon it, and brings forth vegetation useful to those for whose sake it is cultivated, receives a blessing from God. But if it bears thorns and thistles, it is worthless and near to being cursed; its end is to be burned." (Hebrews 6:4-8 RSV)
Fact Finder: Will the earth one day be as "full of the knowledge of The Lord as the waters cover the sea"?