# Competing Hypotheses

> Analysis of Competing Hypotheses (ACH). Use when investigating any entity, anomaly, root cause, or claim that could have multiple explanations — fraud vs error, bug vs design, correlation vs causation. Dispatches parallel agents with opposing hypotheses, then synthesizes the surviving explanation. Based on Richards Heuer's CIA methodology.

- Skill: `markusstrasser/competing-hypotheses` (Agent Skill)
- Install (CLI): `npx skillmds@latest add markusstrasser/competing-hypotheses`
- Raw SKILL.md: https://api.skillmd.com/api/skills/markusstrasser/competing-hypotheses/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: markusstrasser (https://skillmd.com/u/markusstrasser)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/markusstrasser/competing-hypotheses

---


# Analysis of Competing Hypotheses (ACH)

You are evaluating a claim, entity, or anomaly. Your job is NOT to confirm the most likely explanation. Your job is to **systematically destroy every possible explanation** and see what survives.

## Core Principle

> "Truth is whatever is left standing after you have relentlessly tried to destroy every possible explanation." — Richards Heuer, *Psychology of Intelligence Analysis*

Evidence consistent with multiple hypotheses is **diagnostically useless**. Only evidence that **eliminates** a hypothesis has value.

## The Process

### Step 1: Generate Hypotheses

For the target `$ARGUMENTS`, generate at minimum THREE competing hypotheses:

| Hypothesis | Description |
|------------|-------------|
| **H1: Wrongdoing** | The anomaly reflects intentional fraud, abuse, or corruption |
| **H2: Legitimate** | There is a lawful, non-fraudulent explanation |
| **H3: Artifact** | The anomaly is a data error, reporting change, or measurement artifact |

Add domain-specific sub-hypotheses as needed.

### Step 1.5: Complexity Gate

Before dispatching agents, assess: can a single agent resolve this with A1/A2-rated sources? If yes, skip ACH — just answer directly. ACH is for genuinely ambiguous cases where the single-agent success rate is below ~45%. Don't use a cannon for a nail.

### Step 2: Dispatch Competing Agents

Launch **three parallel agents** (Task tool with subagent_type="general-purpose"). **Use different models when available** — same-model debate is a martingale for correctness (ACL 2025, arXiv:2508.17536). Different models have different failure modes, biases, and blind spots:

- **Agent A — Prosecution** (prefer Gemini — different training biases): Search for enforcement history, ownership anomalies, financial pressure, fraud signatures. Tag all claims [SOURCE: url] or [INFERENCE].
- **Agent B — Defense** (prefer GPT — different blind spots): Search for policy changes, industry trends, M&A, comparable clean entities. Find the BEST innocent explanation.
- **Agent C — Artifact Investigator** (Claude — strong at structured analysis): Search for data reporting changes, known data issues, system migrations, whether anomaly appears in multiple independent sources.

If multi-model dispatch isn't available, same-model agents still have value via the diagnosticity matrix — but the adversarial pressure is weaker.

### Step 3: Build the Diagnosticity Matrix

```
| Evidence                  | H1 | H2 | H3 |
|---------------------------|:--:|:--:|:--:|
| [evidence item]           | C  | I  | N  |

C = Consistent, I = Inconsistent, N = Neutral
```

**Key rule:** Evidence that is C/C/C has **zero diagnostic value**. Focus on evidence that eliminates hypotheses.

### Step 4: Score and Synthesize

**Recitation first:** Before scoring, each agent restates its top 3 most diagnostic evidence items verbatim. This combats lost-in-the-middle effects when synthesizing across agents (Du et al., EMNLP 2025: +4% on RULER, training-free, model-agnostic).

Count strong inconsistencies per hypothesis (weight by source grade: A1 = strongest, F6 = weakest). The surviving hypothesis has the fewest strong inconsistencies.

```markdown
## ACH Result: [Entity/Anomaly]

**Surviving Hypothesis:** [H1/H2/H3 + description]
**Confidence:** [0-100]%
**Key Discriminating Evidence:**
- [Most diagnostic item] — eliminates [H2/H3] because [reason]

**Residual Uncertainty:**
- [What evidence would flip the conclusion]
- [What data we don't have]
```

### Step 5: Red Team (recommended for high stakes)

Dispatch a fourth agent to ATTACK the surviving conclusion: find missed evidence, alternative explanations, source quality weaknesses, what a defense attorney would argue.

## When NOT to Use

- Simple factual lookups
- Clearly confirmed findings with A1-rated sources
- Time-critical situations where speed > rigor

$ARGUMENTS