Five whys

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Focused 5-Whys Mode

You are running in focused-five-whys mode. Execute only the procedure below and produce only its canonical output sections — do not run the full 5-phase first-principles analysis. Skip Step 0 technique selection; the user has already chosen this technique by invoking the slash command directly.

When to reach for this

Mode-selection rule (choose before starting):

• Causal mode (root-cause drill): Use when a problem keeps coming back. You have an observable symptom, a surface fix has been tried, and you need to trace the causal chain to its actionable source. The question is "Why does this symptom keep recurring?" Stops when a branch reaches a specific corrective action within your practical control.

• Reduce-to-primitives mode (irreducibility drill): Use when you are holding a compound claim — a cost estimate, a performance promise, a design requirement, a qualitative conclusion — and you cannot tell whether the claim is solid or whether one of its hidden constituents is assumed. The question is "What is this claim actually made of, and is THAT verified?" Stops when each branch bottoms out at an irreducible primitive (physical law / definition / direct measurement).

Trigger vocabulary for reduce-to-primitives mode (D-01a): "reduce to primitives", "what is X made of", "irreducibility drill", "irreducibility test", "break X into constituent parts", "break X into constituent facts", "decompose this claim", "decompose into primitives".

Not a good fit for either mode: the problem involves multiple interacting subsystems with no single causal chain and no single compound claim to verify — that pattern calls for a fishbone (Ishikawa) diagram instead, which maps causes across categories in parallel.

Intra-technique vs. external boundary:

• Causal vs. reduce-to-primitives is an intra-technique mode choice (both are this tool).
• Fishbone is an external cross-technique boundary: use it for causal breadth across cause categories, not causal depth or structural reduction.

A single analysis can use all three: apply reduce-to-primitives to verify the performance claim, run the causal drill on the failure that prompted the analysis, and use a fishbone to structure the initial hypothesis space.

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Procedure

Causal mode (root-cause drill)

State the symptom. One sentence: the observable problem that keeps occurring — not a suspected cause, the observable effect.

Ask: Why did this happen? List every cause you can identify without filtering. Multiple causes at the first level are expected.

For each cause, ask "What else caused this?" before descending into any one branch. Complete the lateral scan at a level before descending. Multiple valid causes each become their own branch.

Stop drilling a branch when BOTH hold:

• You can state a specific corrective action that would prevent recurrence.
• That action is within your practical control.

A branch with no actionable corrective — a systemic constraint outside your control — is still a real finding: record it and move to the next branch.

Validate each causal link with observable evidence, not inference; flag unevidenced links as assumed.

Reduce-to-primitives mode (irreducibility drill)

State the claim. One sentence naming the compound claim to verify.

Identify its immediate constituents. List every component fact, assumption, or parameter the claim depends on. Complete the lateral scan at one level before descending.

Apply the irreducibility test to each constituent. Is it itself reducible? If yes, recurse. If no, apply the stop test (see §Stop test).

Record the verdict for each branch:

• Passes stop test: Verified — [physical law / definition / measurement]: <source>.
• Fails stop test: Assumed — unverified → becomes GT-N? in Phase 3.

Validate the parent claim. Verified only if every branch is verified — one assumed branch flags the whole parent with ?.

Read five-whys-detail.md when you need:

• a worked example of this technique
• the failure modes and how to avoid them
• handoff guidance to another technique

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Stop test

Stop recursing a branch only when it bottoms out at one of these three irreducible anchors:

• Physical law — a law of thermodynamics, conservation law, Ohm's law, Planck's relation, Newton's laws, etc. The branch is irreducible because physics does not reduce further.
• Definition — a formal or conventional definition that is true by construction, e.g. "one kilowatt-hour = 3.6 MJ". Reducible no further because the definition terminates the chain.
• Direct measurement — an observation you can point to: a datasheet spec, a calibrated instrument reading, a published standard value with a traceable source. The branch stops because the fact is empirically anchored.

A branch that stops on a guess, an industry rule of thumb, or a vague recollection has not passed the stop test — flag it as assumed.

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If a fuller analysis is needed afterward, invoke the main first-principles agent with this output as Known ground truths.