Copyleft: Jaakko J. Wallenius with Creative Commons 2.0

“Imagine there's no heaven
It's easy if you try
No hell below us
Above us only sky
Imagine all the people
Living for today...

Imagine there's no countries
It isn't hard to do
Nothing to kill or die for
And no religion too
Imagine all the people
Living life in peace...”

-John Lennon in "Imagine" (1971)

Some of my own thoughts on the quote:

I was sitting in the garden, and I watched as a small plane flew over me. I thought how nice it would be to be able to fly and be free. However, at that same moment I realized that aviation is the most heavily regulated form of human activity there is.
You must learn an incredible number of rules and restrictions to be able to fly. All this is also incredibly costly. I did also realize at that very moment that human imagination can soar in the sky where it likes, when it likes and without asking anybody for permission. It does not cost a penny to fly in your imagination.
A silly and childish thought, I freely admit. In the modern world you need to climb that mountain, dive that cave and run that desert to be able to feel them. However, in the times when people did not have the money and resources to do these things, the voyages of imagination were valued in a different way.

http://en.wikipedia.org/wiki/Imagine_(album)
"Imagine is the second album by John Lennon. Recorded and released in 1971, it tended towards songs that were gentler, more commercial and less avant-garde than those on his previous album, the critically acclaimed John Lennon/Plastic Ono Band. The album is considered the most popular of his works. In 2012, Imagine was voted 80th on Rolling Stone magazine's list of the "500 Greatest Albums of All Time".