Every now and then you come up with an idea that's so stupid it's profound. Maybe you're about to fall asleep, under the influence of something wacky, or you're in the shower, but sometimes wisdom just strikes. You can't predict when it will happen and you can't identify where it comes from, but it just dawns on you. Perhaps it's divine intervention.
You suddenly realize that there's no way to know if everyone sees colors the same. Or you realize that if a monkey sat down at a typewriter for infinity, not only would he eventually type out all the works of Shakespeare, but he'd also write your full life story with the exact details of your death before you even know them. These ideas just happen to you and all you can do is share them. That's what all of these brilliant posters did, and boy is the world better for it.