The Assumption Hunter: Uncover Hidden Premises

What Are Assumptions in Arguments?

An assumption is what an argument treats as true without proving or stating. It’s the foundation the argument builds on — invisible but essential. If the foundation is weak, the whole structure is unstable, no matter how elegant the reasoning above it.

Consider: “We should invest more in public transit because it reduces traffic congestion.” This sounds reasonable. But it assumes congestion is a problem worth solving, that transit will actually be used if built, that the cost-benefit ratio favors transit over alternatives, and that the speaker’s definition of “investment” matches yours. None of these are defended — they’re assumed.

This doesn’t make the argument wrong. But it explains why someone who doesn’t share these assumptions won’t be persuaded, even if the logic is flawless. Arguments fail at the assumption level more often than at the logic level.

The skill to find assumptions in argument is what separates readers who get convinced from readers who understand why they’re being asked to be convinced.

Three Types of Hidden Premises

Assumptions come in three flavors. Recognizing the type helps you decide what to do about it.

Factual assumptions are unstated claims about reality. “Electric vehicles reduce emissions” assumes the electricity grid is cleaner than gasoline — which depends on where you live. Factual assumptions can be verified: look up the data.

Value assumptions are beliefs about what matters or is good. “We should prioritize economic growth” assumes economic growth is the right goal. Value assumptions can’t be verified — you either share them or you don’t. But making them explicit lets you disagree consciously rather than accidentally.

Logical assumptions are reasoning steps the argument skips. “Crime rates dropped after we hired more police, so more police reduce crime” assumes the correlation is causation. Logical assumptions hide in the gaps between evidence and conclusion.

The Prompt in Action: Examples

Let’s run PR020 on a sample argument: “Companies should require employees to return to the office because in-person collaboration drives innovation.”

What must I believe for this to be persuasive? That innovation is primarily driven by in-person interaction. That the kind of collaboration that happens in offices can’t be replicated remotely. That innovation is the primary metric for evaluating work arrangements.

What evidence is presented vs. assumed? Presented: none, actually — this is assertion, not evidence. Assumed: that in-person work correlates with innovation, that current remote innovation rates are insufficient.

Alternative explanations not considered? Innovation might be driven by hiring practices, incentive structures, or project selection — not location. Remote work might enable different kinds of innovation.

Who finds this convincing, who doesn’t? Convincing to: executives who built careers on in-office work, people who associate physical presence with productivity. Unconvincing to: people whose best work happens in isolation, those with data showing remote innovation success.

Follow-Up: What to Do with Assumptions

For factual assumptions: Verify. If the argument assumes X is true, check whether X is true. Use the Fact-Check Mode guide.

For value assumptions: Decide consciously. You don’t have to reject arguments whose values you don’t share, but you should know you’re adopting their values when you accept their conclusions.

For logical assumptions: Examine the leap. Is the jump from evidence to conclusion justified? Are there alternative explanations?

Identify load-bearing assumptions. Not all assumptions matter equally. Some are peripheral — if wrong, the argument weakens but survives. Others are load-bearing — if wrong, the entire argument collapses. Focus your verification energy on the latter.

Connecting to Your Critical Reading Toolkit

The Assumption Hunter works best in combination with other Critical Reading prompts:

Before assumption hunting: Use the Argument Mapper (PR007) to see the explicit structure first.

For deeper context: The What’s Missing prompt identifies gaps that may hide additional assumptions.

For source comparison: The Compare Two Articles guide helps you see which assumptions are shared across sources and which are contested.

You’ve completed the Critical Reading pillar! Return to the AI for Reading hub to explore other pillars.