To business:


In a 2002 Pentagon briefing, then U.S. Secretary of Defense Donald Rumsfeld famously said:
"Reports that say something hasn't happened are interesting to me, because as we know, 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 — the ones we don't know we don't know.
And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones."
It wasn't typical media material. It even won Rumsfeld the "Foot in Mouth" award from the Plain English Campaign in 2003. But the idea of unknown unknowns has endured.
Awareness—Understanding
When placed in a 2x2, somewhat like I have done, some people have referred to it as the Rumsfeld Matrix, or the Awareness—Understanding Matrix. I prefer diving straight into Unknown Unknowns as they're the crux of it.
For example, say you plan to start a café:
Unknown Knowns
What you know is knowable, but you don't know it, yet
You can find data on the market, the costs, and potential customers. These things can be known through research—others know them—but you didn't know them.
Known Knowns
What you know you know
Your costs, your product, your route to market, everything you learned in your research. You make your plan around these.
Known Unknowns
What you know you don't know
How people will respond to your product, how fast sales will be, and whether your rent will change.
Unknown Unknowns
What you didn't know you didn't know
Just as you launch your café, Starbucks moves in next door, or we hit a global pandemic.
It's what you don't know that you don't know that gets you. After all, if you knew it, you'd have prepared for it.