It is not an attainment or an achievement. It is a homecoming. Your senses give you the impression that you are experiencing the outside, but you have never experienced the ouside. When you realize that all that all that you experience is within, that absolute homecoming is enlightenment.
The reason why everyone is not naturaly enlightened is simply this: people have categorized the world into good and bad, God and Devil, high and low, sacred and filthy, pure and impure, heaven and hell. These are parallel lines that will never meet. Once you have fractured this existence within yourself, there is no way to react a state of enduring well-being and freedom. You have been told to love your enemy. If you first label someone your enemy and then try to love him or her, its'g going to be torturous! Once you have fragmented creation like this, there is no way to arrive at a state of absolute inclusiveness.
If you believe that someone "up there" is going to rescue you and solve all your problems, just remember that you are living on a round planet -- and one that's spinning. So, whenever you look up, you are obviously looking in the wrong direction! In this vast ever-expanding cosmos, what's up and what's down? You have no clue.
"The only way out is in." -- what does this even mena (( from Adiyogi.??
~sadguru.