Hidden Assumption Extraction¶

Why It Matters¶

The most powerful way to challenge an argument isn't to dispute its stated premises (which are usually chosen to be defensible) but to expose its hidden assumptions. These are often the weakest points because they weren't examined by the arguer. Hidden assumptions also reveal what the arguer takes for granted - their worldview's foundational commitments. Making these explicit transforms unproductive debates about conclusions into productive debates about underlying assumptions.

The Key Move¶

Given premises P₁, P₂...Pₙ and conclusion C, ask: "Even if all stated premises are true, what else must be true for the conclusion to follow?" Look for category jumps (premises about X, conclusion about Y - what connects them?), normative leaps (premises about what is, conclusion about what should be), and quantifier shifts (premises about some, conclusion about all). State the hidden assumption explicitly and evaluate it independently.

Classic Application¶

Economic policy debate. "Raising minimum wage increases labor costs [P1]. Higher costs reduce profits [P2]. Therefore minimum wage kills jobs [C]." Hidden assumptions: [H1] Businesses operate at optimal employment levels. [H2] Labor cost increases can't be absorbed by reducing other costs or accepting lower profits. [H3] Demand doesn't increase when workers have more money. Exposing these transforms debate from "for or against minimum wage" to "which assumptions hold in which contexts."

Surprising Application¶

Career advice. "You're talented at X [P1]. There's demand for X [P2]. Therefore you should do X professionally [C]." Hidden assumptions: [H1] Being talented at something makes it fulfilling. [H2] You can sustain motivation in X long-term. [H3] There aren't better opportunities where you're more talented or demand is higher. Making these explicit prevents optimizing for the wrong variables.

Failure Modes¶

Infinite regress - every assumption rests on further assumptions; you must stop somewhere. Uncharitable reading - inventing ridiculous assumptions the arguer clearly doesn't hold. Assuming hidden assumptions are always false - sometimes they're true but unstated because they're widely shared. Missing the distinction between necessary assumptions (required for validity) and sufficient assumptions (would make it valid if added).

Go Deeper¶

Fisher, "Critical Thinking: An Introduction" (Chapter 4); Scriven, "Reasoning" on assumption identification