Assumptions and Implicit Reasoning

What an Assumption Is

An assumption is an unstated premise that must be true for an argument to work. "Students who take AP classes get into better colleges" silently assumes AP classes actually influence admissions rather than merely correlating with them. To surface assumptions, ask: what must be true for this conclusion to follow from this evidence?

The Negation Test

To verify a necessary assumption, negate the candidate statement. If the argument collapses, it was necessary; if the argument still works, it was not. For "organic food is healthier because it has no pesticides," negate: "absence of pesticides does not make food healthier." The argument falls apart, so the pesticide-health link is a necessary assumption.

Question Stems

Assumption questions read: "the author's argument assumes...," "the argument depends on the assumption that...," or "which is a necessary condition for the conclusion?" The credited answer is the bridge between evidence and conclusion -- typically modest in scope. Grand, sweeping statements usually fail the negation test because the argument survives without them.

Key Takeaways

• Assumptions are unstated premises bridging evidence to conclusion
• Negation test: negate the choice; a necessary assumption collapses the argument
• Necessary assumptions are modest -- extreme statements rarely qualify
• Correlation-to-causation leaps hide the most common assumptions