[Moneyherd]

“There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – there are things we do not know we don't know. ” The Johari Window - quote from Donald Rumsfeld

This is the point of user acceptance tests - it doesn't matter if the code does 100% what it was designed to do. If the users can't make it work, it's no good.

Nice analysis from Codecademy.

[gmaslov]

I love that quote. In a way, this article is talking about the "unknown knowns" -- the things that are so obvious now that you don't even remember learning them, or can't imagine not knowing them. These are the lurking biases and preconceptions that we aren't even aware of having, and may be just as dangerous as the "unknown unknowns".

[slaundy]

Great quote—thanks for sharing it!