The paradox of “known unknown” that characterizes our quest for knowledge has different meanings for different cultures and historical periods. For most philosophers from Plato to Descartes knowledge is a result of human reflection and not of human perception. The Cartesian dualism between mind and body reflected by the dictum “Cogito ergo sum!” makes mind more certain than matter, and knowledge the result of thinking. In this perspective, the “known unknown” reflects the gaps in our rational knowledge about the world, the gaps we are aware of. When we reverse the angle of analysis, and look at the internal world, the “unknown knowns” refers to the tacit knowledge that integrates our experience, intuitions, emotions, values, and ideals. The purpose of this chapter is to distill the content of the “known unknown” paradox and to extract some significant ideas about knowledge understanding.
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During the U.S. Department of Defense News briefing on February 12, 2002, Secretary Donald Rumsfeld was asked to discuss if there was any evidence to indicate that Iraq had attempted to or was willing to supply terrorists with weapons of mass destruction. There were some reports saying that there was no evidence of a direct link between Baghdad and some of the terrorist organizations. Since the lack of evidence concerning some facts was not equivalent with the evidence of inexistence of those facts, Rumsfeld tried to formulate a generic answer that became famous due to the many critiques and debates following that press conference (Rumsfeld, 2002):
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 one.
These expressions “known unknowns” and “unknown unknowns” generated a lot of critiques and debates from many journalists, writers, language experts, philosophers and people involved in aerospace engineering, economics and politics. A simple search on Google done on January 10, 2014 showed 6,460,000 entries for the expression “known unknowns”, and 4,590,000 entries for the expression “unknown unknowns” that reflects the high interest of people in this debate. Inspired by all of this, Rumsfeld published his memoirs under the title Known and Unknown: A Memoir. In the Author’s Note, Rumsfeld (2011) explains the meaning of these expressions. Known knowns refer to facts, rules, principles and laws that we know with certainty. Known unknowns refer to some gaps in our knowledge about the world, but we are aware of them. Unknown unknowns refer also to the gaps in our knowledge, but gaps that we don’t know that they exist. Genuine surprises may be included in this category.
Immediately after that press conference, Rumsfeld was criticized for abuse of language by the Plain English Campaign giving him the Foot in mouth award for the most baffling statement by a public figure. Geoffrey K. Pullum, professor of linguistics at the University of Edinburgh, remarks on his blog that there is nothing wrong with this quotation from linguistic or logic point of views (Pullum, 2003): “The quotation is impeccable, syntactically, semantically, logically, and rhetorically. There is nothing about its language at all”. Moreover, he considers that in our knowledge about the external world there are always areas of knowledge that we are aware of, and areas of ignorance that we are aware of. That reminds him about an old Persian saying:
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He who knows not, and knows not that he knows not, is a fool; shun him.
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He who knows not, and knows that he knows not, can be taught; teach him.
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He who knows, and knows not that he knows, is asleep; wake him.
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He who knows, and knows that he knows, is a prophet; follow him.
In defense of Rumsfeld, John Quiggins, professor of economics at the Queensland University, explains that in decision theory we assume that the decision maker has foreseen every relevant contingency. Based on this assumption, making the right decision becomes a matter of the mathematical algorithm used. We attach probabilities to each of the contingencies, and utilities coefficients to each of the contingent outcomes that will result from a given course of action. Whatever course of the action yields the best average outcome, that is the right decision to make. However, in the real life one cannot foresees all possible contingencies, and that is the meaning of the “unknown unknowns” Rumsfeld is talking about. Also, Quiggins emphasizes the fact that the linguistic formulation is correct and expresses an important aspect of our knowledge: “Although the language may be tortured, the basic point is both valid and important” (Qiggins, 2004).