Check your work: Test eight fictional arguments by searching for counterexamples

Staged checking material

Answer key

1. D1 is valid by category chaining: mirk → doven → pale. D2 is invalid because the blue nim need not be a tora.
2. D3 is valid: the existing round jar is necessarily not a pelt. D4 is valid: the existing siv that is a lon inherits quietness.
3. D5 is valid: rens are within veks, and veks exclude tall things. The conclusion does not require any rens to exist.
4. D6 is invalid because the two ‘some’ premises may describe different abels. Two witnesses provide the counterexample.
5. D7 is invalid because being separately disjoint from fens does not make cados and gors disjoint from each other. D8 is invalid because a property of hups cannot be extended to every kel.
6. A correct invalid justification must make all premises true and the conclusion false. A merely strange story, a fact dispute or ‘I do not believe the premise’ does not test validity.

Scoring rule

For each of eight cards, award 1 point for the correct valid/invalid classification and 1 point for an adequate proof chain or explicit counterexample: 16 points total. A classification with no justification can earn at most 1 point. For invalid cards, the counterexample must satisfy every premise while falsifying the conclusion; for valid cards, the chain must identify the forcing premise relationship. Report classification/8, justification/8, total/16, confidence and error types. A high score demonstrates only performance on these forms, not general intelligence, factual truth or sound high-stakes judgment.

Authority boundary: A governed step-by-step lesson may be completed independently inside its stated limits.