Any "Imagination" that is not rooted at least in a distant possibility of reality is a fairy-tale.When any of the idealists here can show me a period in human history that Lennon envisions, I will humbly aquiesce.
.
I don't believe there has ever been such a period in history. BUT, that being said, I have happily for my entire life, been a Christian. And Jesus' teachings tell us that we SHOULD strive for peace and kinship with our fellow man. I guess maybe if you're an atheist (or just don't listen to Christ?) you can just shrug off all those teachings, that ask us to be better, essentially to imagine, and treat people accordingly.