Single Cause
Also known as: causal oversimplification, fallacy of the single cause
Assuming a complex outcome has one single cause, when many factors contributed.
Examples
A software project ships three weeks late, and the team runs a retrospective.
Manager: “This slipped because Marcus took too long on the API integration.”
Marcus’s part did run long. But the retro also turns up a scope change added in week two, a two-week vendor delay on test hardware, and a holiday nobody planned around. Pinning the whole delay on one person erases everything else that contributed.
The same shortcut shows up in online debates about social trends:
Comment: “Youth crime is up in this city — it’s because kids are playing more violent video games now.” Reply: “Guess we can ignore the school closures, the after-school program cuts, and the factory layoffs, then.”
Video game habits might be one thread among many, but treating them as the explanation ignores everything else changing at the same time.
Why the reasoning fails
Single cause reasoning picks one contributing factor out of many and promotes it to sole explanation, usually because it’s the most visible, the most emotionally satisfying, or the easiest to blame. Complex outcomes — a late project, a shift in crime rates, an economic downturn — are almost always the product of several factors interacting, not one lever. The fallacy isn’t in naming a real contributing cause; Marcus’s slow work and video game habits might both be real. The failure is stopping there and treating one true partial cause as the complete story, which leads to fixes that only address a fraction of the problem.
How to respond
- Ask what else contributed: “That’s probably part of it — what else was going on at the same time?”
- Name the pattern: “This sounds like more than one factor. Can we list them out?”
- Watch for the most convenient explanation winning by default. The cause that’s easiest to blame isn’t automatically the biggest one.
- Don’t overcorrect into “everything is equally responsible” either. Some factors really do matter more than others — the goal is a weighted picture, not a refusal to say anything caused anything.