Key Assumptions Check

Definition

The key assumptions check is a structured method for identifying and challenging the unstated, often unconscious premises on which analysis and planning depend. Analysts and planners operate under many assumptions—some explicit, most hidden. This technique makes the hidden visible, then tests each assumption: Is it necessarily true? Under what conditions might it fail? What new information would invalidate it? The process is most valuable early in a project, but can be applied at any stage before finalizing judgments.

In the Book

The handbook describes hidden assumptions as "ideas held—often unconsciously—to be true and, therefore, seldom examined and almost never challenged." The technique has four steps: First, write down the current analytic line or plan premise so all can see it. Second, articulate all premises—stated and unstated—that must be true for this line to be valid. Third, challenge each assumption: why must it be true? Does it hold under all conditions? Fourth, refine the list to only those assumptions that truly are essential, and identify conditions or information that might undermine them.

The handbook includes probing questions: How confident are we this assumption is correct? What explains that confidence level? What circumstances or information might undermine it? Is this a key assumption or a key uncertainty? Was it true in the past but less so now? If it proves wrong, would it significantly alter our conclusion? The process often identifies not just flawed assumptions but new factors that warrant further analysis. The handbook notes this is especially difficult because we make assumptions without realizing it, and our brains resist examining the foundations of conclusions we've already adopted.

Why It Matters

Plans and analyses rest on a foundation of assumed facts that go unexamined. Key assumptions check forces that foundation into view. A plan that assumes the adversary will behave rationally, or that supply lines will remain open, or that organizational culture will support change—each is making bets. Surfacing them early allows the organization to either validate the assumption, accept the risk it carries, or redesign the plan to reduce dependence on it. This concept recognizes that the most dangerous failures are those rooted in things we didn't even know we were assuming—not in things we knew were risky and decided to accept.