"Imagine" as its so often called refers to a Song that has been interpreted in various ways, criticized, revered and even worshipped. The deceptively simple to understand lyrics and soothing music have probably contributed to its popularity in the 20th Century.
While many people have equated it to a communist recruitment song, it may indeed be a much bigger idea. In fact, you can imagine,whatever you want the song to mean.
The very idea of a world with "Nothing to kill or die for" is so appealing to any human being irrespective of her religion, political ideology, country etc... its surprising that we still live in a world torn apart by war and strife.
This probably is due to the human need to have something to kill or die for, a purpose for life even. Unless we have a different more attractive reason to "live for", we may just have to be content with dreams.
Only part of the song that baffles me is a "A brotherhood of man", why not a sisterhood of women? or better still a "Fellowship of Humanity"(this is actually the name of a church). One can only hope that, Lenon used the word brotherhood to mean "a group of people or all people"
A world with "no possessions" can be "Imagine"d today only as part of communism. Human pursuit of materialism can just be that "a pursuit". The irony of it was "probably" not lost on Thomas Jefferson who put "Life, liberty and the pursuit of happiness" in the US declaration of Independence. As the human race moves ahead it may "someday" come to realise that as long as we have greed we will have hunger "And the world will live as one".