Think Five Whys

Five Whys

Five Whys traces a problem to a root cause by asking "why?" of each answer, about five times, until you reach a cause worth fixing. It is famous and frequently requested, and its evidence is weak: the critical literature finds it flattens multi-cause problems into a single chain and discards the rest. This skill runs Five Whys honestly. It leads with that caveat, then forces the one discipline a bare why-chain omits and that makes it safe to run at all: at each step, flag whether more than one cause could apply, and the moment the problem is multi-cause, say so and hand it to think-issue-tree. The output is a single linear why-chain with a branch-or-not flag on each step plus one countermeasure aimed at the terminal node, not a confident single root cause presented as the cause.

Before you run this: the evidence caveat

Five Whys is tier X (weak or contradictory evidence). The governing critique is Alan J. Card, "The problem with '5 whys'," BMJ Quality & Safety 26(8) (2017): 671-677, which argues the technique oversimplifies complex problems, follows a single causal chain when failures are multi-causal, and limits understanding of how processes actually fail; Card's prescription is to move to branching, systems-oriented causal-tree diagramming. John Allspaw, "The Infinite Hows (or, the Dangers of the Five Whys)" (2014), adds that in socio-technical systems the linear "why" chain drifts toward a person and a counterfactual (the "Bad Apple" blame trap) and recommends "how" over "why" to recover the multi-contributor picture. The method is reliable only for simple, linear, single-cause failures; beyond them its output looks like THE cause when it is one cause among many.

So a single chain is not a verdict. If you run Five Whys here, the value is not the chain, it is the discipline this skill adds: flagging at every step whether more than one cause could apply, and stopping to redirect when it can. For any problem that might have more than one cause - which is most real problems - think-issue-tree is the stronger move: it branches with MECE-plus-remainder discipline instead of forcing one path. Do not report a single root cause as the answer to a many-cause problem, and do not invent quantified claims about Five Whys' effectiveness (none are supported).

When to Use

• The user asks for Five Whys (or "5 whys") by name and you should run it honestly rather than refuse.
• The failure is plausibly a simple, linear, deterministic chain (a machine fault, a single procedural slip) and you will still flag any branch points you hit.
• As a fast teaching prompt for the habit of not stopping at the first explanation, with the multi-cause caveat attached.

When NOT to Use

• When the problem may have more than one contributing cause (the documented failure mode): use think-issue-tree, which branches instead of forcing a single chain.
• When the failure is socio-technical and the chain would terminate at "operator error" (the Bad Apple blame trap): use think-issue-tree to keep the conditions, not the person.
• When you need a reproducible, coverage-checked decomposition rather than one investigator's single path: use think-issue-tree.

Instructions

When asked to run a Five Whys, follow these steps:

1. Lead with the caveat. State up front that Five Whys' evidence is weak (Card 2017) and that the value is the branch-flagging discipline below, not the chain itself.
2. State the problem precisely. One concrete, observable symptom - the thing that actually went wrong, not a vague theme.
3. Ask "why?" and answer once. Take the answer as the next link. Then ask "why?" of that answer. Repeat, roughly five times, until you reach a cause you could actually act on.
4. At every step, flag the branch. Mark each link [single cause] (you are confident this is the only "why" that matters here) or [branch] (more than one cause could legitimately apply). A [branch] is an honest admission that you are discarding alternatives by walking just one.
5. Check for multi-cause before you commit. If any step is [branch], or if the failure is socio-technical, stop: say so plainly and recommend think-issue-tree rather than presenting the chain as the answer.
6. Name one countermeasure at the terminal node. Aim the fix at the terminal cause, not the original symptom - and only if the chain held as [single cause] throughout.
7. Emit the linear chain with branch flags plus the countermeasure per references/TEMPLATE.md.

Output Format

Use the template in references/TEMPLATE.md. The deliverable is the single linear why-chain with a branch-or-not flag on each step, a terminal root cause, and one countermeasure, with the caveat leading - not a confident single root cause stripped of its alternatives.

Quality Checklist

Before finalizing, verify:

• [ ] Leads with the evidence caveat (Card 2017) before the artifact; does not overclaim the method's value.
• [ ] Each step is flagged [single cause] or [branch].
• [ ] If any step is [branch] (or the failure is socio-technical), the output says so and redirects to think-issue-tree instead of presenting the chain as the cause.
• [ ] When the chain is genuinely single-cause, it terminates at a cause you could act on (not a convenient symptom); when it branches, it stops honestly instead of forcing a terminal cause.
• [ ] A countermeasure is aimed at the terminal node when the chain is single-cause; when it branched, no countermeasure is forced and the problem is handed to think-issue-tree.
• [ ] No invented quantified claim about Five Whys' effectiveness appears.

Evidence

Tier X (weak or contradictory evidence; normally would not ship). It ships as a contested lens, caveat-first and explicit-request-only, because users ask for Five Whys by name and an honest run that leads with the deficiency and adds the missing branch-flagging discipline beats a flat refusal. The governing critique is Card (2017): the single-chain technique oversimplifies multi-causal problems. Allspaw (2014) documents the socio-technical blame trap. Evidence is transferred from human investigators in manufacturing, healthcare, and software operations, not AI-validated; Five Whys' distinctive single-chain shape has no controlled support, and the better move (think-issue-tree) already ships. Full grading: evidence/dossier.md.

Examples

See references/EXAMPLE.md for a completed Five Whys chain with branch flags and a terminal countermeasure.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: product-on-purpose
• Source: product-on-purpose/thinking-framework-skills
• License: Apache-2.0
• Homepage: https://product-on-purpose.github.io/thinking-framework-skills/

Install and usage instructions live in the source repository linked above.