Double Crux
A CFAR technique for resolving disagreements by collaboratively finding the underlying belief (the "crux") that drives both parties' positions. A crux is a fact that, if believed differently, would change your conclusion.
Three Modes
- •Design Mode — Prepare for a disagreement by mapping belief structure and identifying likely cruxes
- •Practice Mode — Walk through Double Crux on a practice topic to build skill
- •Execute Mode — Facilitate real-time Double Crux on a live disagreement
Prerequisites
Double Crux requires: genuine willingness to change one's mind, excitement about getting closer to truth, emotional safety, and epistemic humility. If prerequisites aren't met, acknowledge this and suggest alternatives.
Core Process
Step 1: Identify the Disagreement
Find a statement A where parties genuinely disagree. Confirm it's real, not semantic.
Step 2: Operationalize
Move from abstract to concrete:
- •Attach numbers: "very likely" → "70% probable"
- •Define observable outcomes: "economy improves" → "GDP growth > 3%"
- •Make claims falsifiable: "How would we know if this were true or false?"
Step 3: Seek Cruxes
Each party independently identifies cruxes — beliefs such that changing them would change their position on A. Key question: "If [belief B] were false, would you change your mind about A?"
A double crux is a belief B where both parties disagree about B AND B causally influences both positions on A.
Step 4: Resonate
Test if cruxes are genuine: "Does this really feel crucial?" / "Would you genuinely change your position?" Filter out pseudo-cruxes (claims that sound important but wouldn't actually shift your view).
Step 5: Recurse
Take the double crux B and repeat. B becomes the new A. Seek crux C. Continue until you reach verifiable factual claims you can look up.
Prep Tool (Design Mode)
Before a difficult conversation:
- •Identify your own cruxes
- •Predict the other person's likely cruxes
- •Find likely overlap
- •Prepare operationalized versions of key claims
- •Enter with genuine curiosity about their reasoning
Solo Belief Examination
- •Pick a belief you hold strongly
- •Steelman the opposing position
- •Identify what facts would need to differ for you to hold the opposing view
- •Research whether those facts are as you assume
- •Update confidence based on findings
Facilitation Prompts
Operationalizing: "Can you make that more specific?" / "Can you put a number on that?" / "What would we observe if you're right?"
Finding cruxes: "What are the key reasons you believe this?" / "If [reason] turned out wrong, would you change your position?" / "What evidence would change your mind?"
Testing: "Hypothetically, if I proved [crux] is false, would you actually update?"
When stuck: "Let's each draw out our reasoning. What beliefs feed into your position?"
Common Failure Modes
- •Pseudo-cruxes: Always test with the resonance check
- •Insufficient operationalization: Force concrete predictions
- •Emotional loading: Start with lower-stakes practice topics
- •Bad faith: Requires genuine truth-seeking from both sides
- •Recursion overload: Stop when it stops being productive
- •Terminal value disagreements: Recognize when you've reached values, not facts