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QLDPhilosophy and ReasonQuick questions
Unit 3: Reason and formal logic
Quick questions on Formal fallacies and invalid forms: QCE Philosophy and Reason
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the undistributed middle?Show answer
In categorical syllogisms, the middle term (the one appearing in both premises but not the conclusion) must be distributed (referring to all members of its class) at least once. The fallacy of the undistributed middle breaks this rule:
What is exposing a formal fallacy?Show answer
To show an argument commits a formal fallacy: (1) symbolise it to reveal the bare form; (2) name the invalid form; (3) give a counterexample with the same form, true premises and a false conclusion. The counterexample is the clinching move, because it demonstrates the form does not preserve truth, regardless of the original content.
What is q1?Show answer
Identify the fallacy and explain why it is invalid: "If she is guilty, she will be nervous; she is nervous; so she is guilty." [3 marks]
What is q2?Show answer
Explain the fallacy of the undistributed middle. [3 marks]
What is q3?Show answer
Distinguish denying the antecedent from modus tollens. [2 marks]
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