I think I’m about to repeat an old thought. It’s yet another play on Donald Rumsfeld’s “unknown unknowns” formulation. But this adds to the unknown unknowns a third and more difficult dimension of mystery: knowable and unknowable.

Rumsfeld’s original quote:

Reports that say that something hasn’t happened are always 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.

I want to expand the “unknown unknowns — the ones we don’t know we don’t know” in to account for two very different reasons we may not know that we do not know something.

Here is my expansion:

• Knowable unknown unknowns — we don’t know that we don’t know because we neglected to consider some relevant thing that, had we considered it, would have made sense to us and enabled us to respond effectively.
• Unknowable unknown unknowns — we don’t know that we don’t know because we are philosophically unprepared or unequipped to notice some relevant thing, so even if we had considered it we would have been unable to make sense of it, and it could not have informed an effective response.