Ever hear of Plato's allegory in the cave? To sum it up, imagine that from birth you and some other people lived in a cave with your head and neck restrained by chains so that you are forced to look at the wall in front of you.
Imagine that there is a fire behind you and people walk by carrying different shapes, the shadows of which are cast on the wall in front of you. To you, this would be reality and you would think the shadows are real.
Imagine, after 20 years, you are unchained and brought up to the light for the first time in your life. You would be almost blinded, confused, but eventually your eyes will adjust and you will come to understand your situation.
How would you feel if you were taken back down into the cave again. Would you feel bad about any others who live in the cave and not experienced the light? Would you be able to come back to the position where you occupied before, that the world is shadows and flickering light? If you tried to convince the other people in the cave that there is another world out there of blinding light, would they believe you, having never experienced the things that you tell them?
In this context, Plato, in the allegory of the cave, is talking about the relationship between knowledge and ignorance.
In whichever state we are in, we have become adapted to it and view everything as "reality" from that perspective. No one has knowledge of the state they are in, except when they are in the process of changing it. Another element that Plato introduces is the concept that there is only one way that one can become knowledgeable, as it is impossible to become more ignorant short of brain damage.
I am here, and right now I feel like those in the cave. I think I know what's going on. If someone were to argue with me about an arbitrary subject like the existence of a specific God like Allah or Jehovah, I am confident that I can hold my own. If someone debates politics with me, I have confidence that my position is more reasonable. Most of the time, this is how I feel. However, being in the cave and being in the light are relative positions. After all, it is quite possible I'll experience some enlightenment or acquire new knowledge that will further illuminate my mind.
The acquiring of new knowledge or the experience of a bizarre revelation or a great idea is the only time where a difference is perceived. The new wrinkle in the brain is the same thing as suddenly walking into the light, a mixture of wonder and confusion, followed briefly by the sensation of understanding and wonder.
However, after we become accustomed to this and adopt the new bit of knowledge to the library in our brain, we revert back into the normal condition until the next revelation. But what happens if I am put in the position which I held before the revelation, or around people that believed what I once did?
For instance, I used to belong to a particular religion. After a Philosophy class, I was imbued with knowledge that enlightened me and led me away from this religion. It was simple logic that showed to me that the belief in specific gods was problematic, especially if the God is all-powerful and all-knowing. Now I don't believe that and it has become second nature to do so.
When I am around people of this religious group, I feel alienated and almost sympathetic for them, because to me it is a delusion that they are living with. I even try to explain it to them. This is like the man who saw the light being led back down to the cave again. It is impossible to get back into the same state of mind because a new bit of knowledge had been acquired, mainly that there is an entirely different world out there. And the people whom I try to explain things to, think I am crazy and delusional.
Someone may say that it is possible to know the objective truth, and if we happen to know that truth, we would always be in the right. I'd argue that by saying that we wouldn't really know, because to think we have knowledge is a state that we always occupy until new knowledge comes by and ruins the thought. So, it is best to keep an open mind and heart, and hear out the various explanations of truth, and adopt only those things that ring true.
So, in essence we are all living in Plato's cave, and if we study and seek knowledge always, we will continuously be enlightening ourselves. If we stay where we are intellectually and don't seek knowledge and truth, it will be as if we are in the cave again. I'm not saying that we will become more ignorant, but that we won't become more knowledgeable.