Have you ever submitted a drawing or a photograph or something you wrote to a contest? Usually there's a theme you have to match, and it's all very rushed and forced, and in the end the arbiters of the contest just accept submissions that serve their preconceived narrative rather than celebrate challenging quality. I have succeeded seldom and been rejected most times in this business. The Beatles wrote "All You Need Is Love" under those kinds of circumstances (except their acceptance was guaranteed, which I'm sure did nothing to make it less unnerving) and just happened to produce a song of significance in world history.
They were commissioned to write and perform a new song for the world's first satellite broadcast - "Our World," which was kind of the Olympics and a TV variety show combined, with countries contributing segments to represent themselves. The Beatles were Great Britain at the time. With less than three weeks before the event, John Lennon began to write in earnest. He was still putting finishing touches on the song the day of the broadcast - to 25 countries and over 400 million people. They had just released Sgt. Pepper's Lonely Hearts Club Band a few weeks before and could've been forgiven if they were a bit creatively spent.
Instead, John Lennon did something that became kind of a template for anyone creating content for worldwide consumption, keeping it extremely simple. He focused on one forceful idea, and he conveyed it in five words. Our international blockbuster movies do the same thing now (using about five words and 500 explosions).
Those are the iconic choruses of "All You Need Is Love."
The verses were much more complex, and I'm sure John took it as his right to say more in the verses if people were going to focus on the choruses anyway. ("Don't bore us, get to the chorus" mentality)
First of all, the verses are in a 7 beat, an anomaly then and really still today in popular music. The beat is slow enough that non music people probably do not notice.
The lyrics are a real work of art, full of both plain meaning and maybe not such plain meaning. His lines are sly repeating variations of the same grammatical format:
"There's nothing you can do that can't be done.
Nothing you can sing that can't be sung."
I have assumed Lennon omitted the word "otherwise" at the end of each line. As in, don't sacrifice love to spend your life doing things that can just be done by others. Careerists and perfectionists, relax, and realize that the more you strive, the more you are shutting out love.
But consider if there isn't an implied "otherwise" ending these lines.
It's most telling in the second verse:
"There's nothing you can know that isn't known.
Nothing you can see that isn't shown."
It's not just that some other person probably knows all the things you know. It's hinting at the idea that knowledge itself resides in completeness elsewhere, beyond human minds. Not only that, but the daily act of seeing the world is not as me-centered as you think it: You are not seeing it - you are being shown it. Suddenly there are bigger spiritual implications.
He's not flashing Bible verses; He is hitting on a reality that many people suppress, religious and atheist: The world is being given to us, shown to us; it is being made available to our senses and reason to be discovered. Everything in front of our eyes is a message.
You can get the same ideas in-depth by reading Thomas Paine's "The Age of Reason." John Lennon decided to hide glimpses of it in the 7-beat verses of his pop song on the world's first international broadcast. It's a hella-catchy song too.