CFAR rationality technique for resolving disagreements by finding shared underlying belief divergence points (cruxes). Use when the user wants to: (1) resolve a disagreement by finding the real point of contention, (2) prepare for a difficult conversation by mapping belief structure, (3) practice collaborative truth-seeking, (4) examine beliefs by finding what would change their mind, or (5) facilitate a structured disagreement between two positions. Triggers: "double crux", "disagree", "what would change my mind", "crux", "resolve disagreement", "find the real issue", "belief examination", "CFAR".
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.
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.
Find a statement A where parties genuinely disagree. Confirm it's real, not semantic.
Move from abstract to concrete:
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.
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).
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.
Before a difficult conversation:
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?"