The Most Philosophical Song You Ever Heard

Todd Rundgren had (was in?  Kinda a fluid concept) a band called Utopia.   

On the album Swing to the Right the song "One World" offers a message of unity between all manner of common people. 

There is more (not Thomas More) but that'll do for now.

I noticed nobody chose Chuck Berry's "My Ding-a-Ling"

I have to agree with Miller about Imagine. Even when I was young it made me cringe.

What is it about grumpy old cynical men? Innkeepers with all the answers. Have no room in their closed minds for Mary or anything that challenges their insular shallow minds. And the irony is the OP's thread ostensibly relates to philosophy. 
Lennon's "Imagine" strikes a chord for hope and a better world. Christianity began as a communal sect. It's growth and success were limited by such a concept so it changed to a more realistic organization. Gained much by doing so but an argument could be made it also lost something important. My interpretation of Lennon's lyrics is they explore the true radicalism of Christ's message.