Weakening by Providing Counterexamples

A counterexample is a specific case that contradicts a general claim. In logic, a single counterexample is sufficient to disprove a universal statement ("all X are Y"). In the more nuanced world of LNAT arguments — where claims are rarely stated as absolutes — counterexamples weaken arguments by showing that the general pattern does not hold in all cases, raising doubts about the reliability of the conclusion.

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The Logic of Counterexamples

Against universal claims

A universal claim asserts that something is true in all cases. A single counterexample disproves it entirely.

Claim: "All democracies have written constitutions." Counterexample: The United Kingdom is a democracy without a written constitution.

The counterexample conclusively disproves the universal claim.

Against general claims

Most LNAT arguments make general claims — that something is usually, typically, or probably the case. A single counterexample does not disprove a general claim, but it does weaken it by showing that exceptions exist.

Claim: "Private schools produce better academic results than state schools." Counterexample: Several state grammar schools and London comprehensives consistently outperform the majority of private schools in league tables.