In February 2002, Donald Rumsfeld, then U.S. Secretary of Defense, delivered what may remain the only enduring philosophical contribution made from a Pentagon briefing room. His now-famous taxonomy of human knowledge—known knowns, known unknowns, and unknown unknowns—was not just a defense of uncertainty in military affairs; it was an accidental masterpiece of epistemology. Much ink has been spilled mocking the speech. Too little has been spent appreciating its raw, uncomfortable truth: that our grip on reality is far less secure than we would like to believe.
Still, after two decades, it is clear that Rumsfeld's framework is incomplete. If we are to take the Rumsfeldian system seriously—and we absolutely should, if only to entertain ourselves during committee meetings—we must extend it. There are more categories of knowing and unknowing than Rumsfeld acknowledged, and without them, we risk misunderstanding the true landscape of epistemology (and of human ignorance).
Let us proceed, with the full seriousness this absurd subject deserves.
I. The Known Known
The Known Known is the sturdy cornerstone of Rumsfeldian epistemology. These are facts that we know, and we know we know them. Gravity exists. The Pacific is larger than the Atlantic. Most conference calls are regrettable.
However, even the Known Known is not as stable as we might wish. History is littered with instances where humanity proudly declared something a Known Known, only to discover it was more of a Wildly Inaccurate Assumption. Medieval physicians knew that bloodletting cured disease; Victorians knew that trains traveling over 30 miles per hour could cause spontaneous human combustion. We know things now too—like the complete range of plausible political beliefs, or that Pluto is not a planet—facts that future generations may regard with affectionate pity.
There is also the danger of Trivial Known Knowns: facts that are undeniably true but carry no discernible value. It is a Known Known, for instance, that a single spaghetti noodle is called a “spaghetto,” or that Canada has a town named “Dildo.” These truths occupy the mind without ever illuminating it, the informational equivalent of polite conversation about the weather.
Thus even within the realm of the Known Known, epistemology demands humility—and perhaps some marinara sauce.
II. The Known Unknown
Next come the Known Unknowns, a category Rumsfeld treated with appropriate philosophical gravity. These are things we are aware we do not know. They represent the respectable side of ignorance—the kind that provokes curiosity, research grants, and poorly attended academic symposia.
Known Unknowns span the profound and the ridiculous. We do not yet know the final Theory of Everything in physics. We do not know what consciousness ultimately is. Nor, on a more pressing level, do we know what happens to socks once they enter a dryer. Are they vanishing into a parallel universe dominated by mismatched gloves and expired Tupperware lids? No one can say, but a dwindling sock population suggests foul play.
Other enduring Known Unknowns include:
Whether the late Queen’s corgis were ever briefed on foreign policy matters.
What the English actually mean when they describe something as “interesting.”
How many times world leaders have hit “reply all” by mistake.
These gaps in our knowledge are neither shameful nor especially urgent. They are the charming mysteries that remind us that even people possessing the most rational minds must occasionally shrug and reach for another biscuit.
III. The Unknown Unknown
The Unknown Unknown is where epistemology grows properly disturbing. These are the things we do not know we do not know—lurking facts, concealed dangers, unimagined possibilities. We cannot seek them because we cannot conceive of them. They fall into our reality like piano crates from the fourth dimension.
History is replete with the catastrophic (and sometimes happy) consequences of the Unknown Unknown. Alexander Fleming didn't set out to find antibiotics; he just noticed some mold killing bacteria by accident. No one at Lehman Brothers in 2007 foresaw that a complex interplay of derivatives and overconfidence would cause global financial mayhem. Prior to 2020, no one predicted that sourdough starter would become a form of social currency.
In cosmic terms, Unknown Unknowns hint at the possibility that our entire universe may be one small province in a vastly larger, utterly incomprehensible reality—possibly one ruled by highly literate sentient mayonnaise, or worse, an interdimensional HOA.
The Unknown Unknowns are unknowable not because they are inherently mysterious, but because they remain, as yet, invisible to our categories of thought. They constitute the dark matter of epistemology: vast, influential, and mostly beyond reach.
IV. The Knowable Unknown
To extend Rumsfeld’s taxonomy properly, we must acknowledge the existence of the Knowable Unknown: facts and truths that we do not currently know, but which are in principle discoverable.
Many historical mysteries fall into this category. Roman concrete, with its remarkable ability to strengthen over centuries, was a Knowable Unknown until recent chemists finally reverse-engineered its secrets. The precise composition of medieval recipes, the engineering marvels of the ancient world, and even the original formula for Coca-Cola—all Knowable Unknowns, simply awaiting the right archaeologist, the right moment, or the right lapse in corporate security.
At a more personal level, Knowable Unknowns include:
The location of your lost car keys, still firmly lodged between the filthy sofa cushions of destiny.
The actual contents of your kitchen’s “miscellaneous drawer.”
The true number of meetings that could, in fact, have been replaced by one-line emails.
Some Knowable Unknowns remain unknown not because of difficulty, but because of apathy or discomfort. There is a species of deliberate ignorance involved: choosing not to read the terms and conditions, not to step on the bathroom scale, not to check the expiration date on that bottle of ketchup in the fridge. In this sense, if the Known Unknown is a noble ignorance, the Knowable Unknown is a somewhat cowardly one—one we maintain because knowing might require action, and action would require effort.
Alternatively, we might actively choose not to know particular things because the knowledge could be painful, inconvenient, or simply too exhausting to confront. Or we superstitiously avoid knowing by not testing for cancer or not checking the oil level in the car, as if seeking to know will cause the harm we fear. These forms of deliberate ignorance are not accidental. They are a quiet pact between ourselves and the universe to leave certain stones unturned.
Sometimes, these are profound, life-altering questions:
Did my best friend hate my speech at his wedding?
Is my boss planning to fire me after this quarter?
Am I really choosing to be single?
More often, they are smaller, daily acts of strategic ignorance, such as “What is actually inside that container at the back of the fridge?”
Choosing not to know allows us to continue living with a certain smoothness. It prevents the mental equivalent of dropping a wrench into our own psychological gears. After all, the world is chaotic enough without having to confirm that, yes, your high school nemesis is now a wildly successful life coach with 1.2 million Instagram followers.
In this sense, the Knowable Unknown is not just a factual gap; it is often also a conscious act of polite self-delusion. We agree not to investigate, not to pull on certain threads. Tacitly, we say that the mystery container will remain forever unexamined, like a moldy Schrödinger’s box of disappointment.
V. The Unknowable Unknown
Finally, we arrive at the Unknowable Unknown: knowledge that, whether due to the limitations of our senses, our minds, or the very structure of reality itself, we will never access.
This category encompasses the concept of the Epistemological Black Hole: truths trapped forever beyond our event horizon of comprehension. They are not merely things we have not discovered; they are things we are not equipped even to imagine.
Consider, for instance, dimensions beyond our three spatial ones. Mathematical models suggest they exist, but our brains are so hardwired for three-dimensional existence that any attempt to grasp higher dimensions produces either fever dreams or mediocre science fiction.
Or take consciousness: it may be that understanding another mind fully is not merely difficult, but structurally impossible. We will never know exactly what it feels like to be a bat, or a dog, or a particularly introspective pigeon.
Other Unknowable Unknowns may include:
· Whether pigeons hold annual strategy conferences about how best to inconvenience humans.
· What happens to the missing socks of the world.
· How many times a day your cat thinks, “I could kill them if I wanted to.”
The point is not merely that we are ignorant. The point is that we are not equipped, and may never be equipped, to remedy that ignorance. It is humbling in the extreme—and also, when we ponder cats, slightly alarming.

Conclusion: The Expanded Rumsfeldian Epistemological Model (EREM)
Thus, the complete Rumsfeldian epistemology stands as follows:
Known Known - Fact that is known and recognized as known
Known Unknown - Gap in knowledge that is acknowledged
Unknown Unknown - Gap in knowledge that is unrecognized and inconceivable
Knowable Unknown - Currently unknown fact that could, in principle, be known
Unknowable Unknown - Truth structurally inaccessible to human knowledge
This expanded EREM framework offers a more honest map of human understanding—a map riddled with blank spaces, trapdoors, and occasionally, misplaced hoisery.
To live well within this epistemology is to recognize both the importance of pursuing knowledge and the inevitability of its limits. It is to admit that we are creatures fumbling through a fog (of war), sometimes finding gold coins, sometimes stubbing our toes, and sometimes—through no fault of our own—wandering straight into a mayonnaise-based civilizational collapse and falling afoul of an HOA.
In the meantime, we might as well sit back to a few sticks of spagetto, down a few espressi, and plan the first EREM conference, to take place in Dildo, Canada at an unknown date in our still unknowable future.
Jerome St Jerome is a part time saint and full-time Bibliophile, living in Vaduz.