Sidney Dekker’s Field Guide to Understanding Human Error sits within reach of my desk, third edition 2014. It’s not the book I quote most often, but the one I most often return to. With every re-reading, what strikes me is how strange it is: written as a guide (subtitle, clear table of contents, plain language) and yet at its core a systematic attack on the standard way of reading incidents.
Dekker’s core operation can be put in one sentence: he shifts the position of judgement – away from above with outcome knowledge, toward the view of those who stood in the moment of action. Old View, in his vocabulary, asks from the outside: who acted wrongly, who failed, who didn’t meet the standard? New View asks from the inside: what was visible, plausible, reasonable to the acting person at that moment, given what they saw, knew, and could put together? The shift isn’t a swap of tools. It’s a shift of the position from which judgement happens at all.
Local rationality. Why “local” is the decisive adjective, not “rational” alone: every actor would be rational, every investigation tacitly assumes that anyway. The word “local” marks something else: the binding to a concrete horizon. Local means what the person could see, know, and combine in the moment, with the indicators in front of them, the pressure at their neck, the training in their head. Dekker’s standard move in the Field Guide is to reconstruct every “wrong” decision from this local horizon first. And the book shows this reconstruction as craft, through concrete incidents, often with transcribed radio logs or witness statements. Little theory, much workshop. In the back of the book there’s a structured question apparatus meant to help any investigation reconstruct local rationality: what did the person have in front of them, what didn’t they, which indicators spoke which language, which ones do they know from training, which resources were available at that moment. This turns a theoretical concept into a workable investigative discipline.
Sharp End / Blunt End. The pair of terms comes from James Reason, and Dekker uses them consistently. Sharp End is whoever stood in the incident: the nurse at the bedside, the operator at the console, the pilot in the cockpit. Blunt End is what created the conditions under which Sharp End works: design decisions, rule sets, resource allocations, trade-offs between safety and speed. Dekker’s point isn’t that the Sharp End is innocent. It’s that most Sharp End actions are responses to Blunt End conditions. Whoever looks only at the Sharp End sees the hand on the lever. And misses the pressure that brought the hand there. And with it the only place where a correction would even be possible.
“Causes don’t exist, you construct them.” Dekker’s sharpest provocation and most frequently misunderstood thesis. It doesn’t mean: everything is equal, everything is relative. It means: what we identify at the end of an investigation as “the cause” is always a selection from many contributing conditions. And the selection says something about the analytical lens we’re looking through. Which factor becomes “the cause” and which stays “context” is a decision of the investigation. A conscious one sometimes, an unconscious one mostly. Dekker’s invitation isn’t to arbitrariness. It’s to self-reflection: what are we doing when we identify a cause? What choice are we making without marking it as a choice?
Causes don’t exist, you construct them.
– Sidney Dekker
What I read differently today
What the book has shaped, after years of practice, can be named pretty precisely: better investigations, more context interviews before the question of blame, less reflex toward “employee sensitisation” as a recommendation. Dekker supplied the vocabulary with which I now turn down assignments where the answer is already prescribed. The limit I notice more strongly with every re-reading: the book is excellent at diagnosis, how to read incidents differently, how to conduct investigations more openly, how to deconstruct the reading reflexes of the Old View. It’s noticeably less explicit on the operational rebuilding question: how to actually build an organisation differently so the New View reading happens not only in investigations but in daily operations. Whoever looks for the next step after the Field Guide typically lands with Conklin (HOP, Pre-Accident Investigations, Operating Principles), more operational, closer to the shop floor. Dekker and Conklin together make the set: first the lens, then the tool.
Who this book is for
Required reading for anyone who investigates incidents or shares responsibility for them: safety officers, auditors, line managers in HRO-adjacent industries, investigation commissions of every kind. Especially for those who notice their investigations were over too quickly, without being able to name exactly why. The book gives the observation a vocabulary. If you read only one book on human error, read this one, not because it gives the most answers, but because it changes the way you ask questions.
Sources
- Sidney Dekker – The Field Guide to Understanding Human Error, 3rd ed., CRC Press 2014 (main source)
- Sidney Dekker – Drift into Failure, CRC Press 2011
- Erik Hollnagel – Safety-II in Practice, Routledge 2018
- Todd Conklin – Pre-Accident Investigations, Ashgate 2012
- James Reason – Managing the Risks of Organizational Accidents, Ashgate 1997 (for Sharp End / Blunt End)