Tacit knowledge is being able to do things without being able to explain how. We can’t learn tacit knowledge from a textbook.2 We know more than we can tell.3

We can make blunders when we use intuition in cases in which we should be relying on scientific analysis. We can also blunder when we rely too heavily on scientific analyses. The statistical analyses that seem so impressive under stable conditions often turn out to be brittle and insensitive to surprises.

Well-ordered domains are structured and stable. We know what causes the effects we want to achieve. We can think systematically about well-ordered domains because we know how they work. We can calculate what decisions to make and how to predict the future. However, we don’t usually live in that world of clarity. Much of the time we find ourselves

We make progress when we find regularities in situations that appeared to be highly complex. We should encourage those researchers who look for order in complex situations. Many hygiene and public health procedures are examples of initially complex domains which, after painstaking study, analysis, data gathering, and assessments, evolved over many

People sometimes make up procedural guides to capture what they think experts are doing. That’s a noble intent, but procedural guides really can’t explain the tacit knowledge that people acquire over decades of experience.

Most of the claims, rooted in well-ordered situations, try to substitute analysis for experience. The claims discourage us from using intuitions based on experience. They seek to replace insights with structured techniques for thinking. But in complex and ambiguous situations, there is no substitute for experience.

Figure 1.1 Three strands of thinking.

Here is another way to teach procedures: Set up scenarios for various kinds of challenges and let the new workers go through the scenarios. If the procedures make sense, then workers should get to see what happens when they depart from the optimal procedures. When procedures are taught in a scenario format, people can appreciate why the procedures

By the time people become proficient, they are seeing situations instead of calculating procedures. Experts rely on their immediate intuitive responses.