Really, truly? The interesting question to me is then: why not? Or how? There are many individuals on the planet who, through no fault of their own, have severely limited mental capacity. You've never met one?
If it helps to clarify: I can't explain relational databases to someone who doesn't have basic numeracy and you can't explain (say) quantum mechanics to me and the hyper-intelligent aliens can't explain ?$%>$£DDDD to you...but none of us in that chain are stupid. And all of us with sufficient power of articulation can convey the elements of those things to each other that matter to the person within their context.