The Bush administration faced three major strategic choices between September 11 and October 7, when the military campaign started: how to define the war, what to do about the Taliban, and what kind of military footprint to deploy. The administration chose to frame the conflict as a War on Terror, to treat the Taliban as of secondary importance, and to adopt a light footprint. The first choice – to declare a War on Terror – has been the subject of ample and justified criticism, then and now. The latter two choices made more sense at the time, and the Taliban’s fall from power two months later, on December 7, seemed to vindicate the administration’s impressive improvisation. But the sense of vindication also numbed the administration to the need to adapt as circumstances changed.

The Rumsfeld knowledge matrix – which spans the knowledge categories “known knowns,” “known unknowns,” and “unknown unknowns” – is used to illustrate the process of model improvement. Two new knowledge subcategories – “poorly known unknowns” and “well-known unknowns” – are introduced to distinguish between accuracy of parameterizations. A distinction is made between “downstream benefits” of parameterizations, which improve prediction skill, and “upstream benefits,” which improve understanding of the phenomenon being parameterized but not necessarily the prediction skill. Since new or improved parameterizations add to the complexity of models, it may be important to distinguish between essential and nonessential complexity. The fourth knowledge category in the Rumsfeld matrix is “unknown knowns” or willful ignorance, which can be used to describe contrarian views on climate change. Contrarians dismiss climate models for their limitations, but typically only offer alternatives born of unconstrained ideation.