Prelims · 8 Mental Ability · 8.12 Syllogism and verbal reasoning

8.12.6 Logical connectives: if–then, only if, unless, necessary and sufficient conditions

Turn every sentence into an arrow P → Q; the only safe moves are forward (P, so Q) and backward through the contrapositive (not Q, so not P); knowing Q or knowing not P tells you nothing.

  • APPSC Group 2 · Prelims
  • Standard level
  • 9 min read
  • Full course

Key terms

  • logical connectives
  • if then
  • conditional
  • contrapositive
  • converse
  • inverse
  • only if
  • if and only if
  • unless
  • necessary condition
  • sufficient condition
  • either or
  • negation
  • De Morgan
  • chain of conditionals

What this note covers

  1. Core factsFoundation
  2. ExplainedStandard
  3. DeeperAdvanced
  4. Common trapsFoundation
  5. Quick revisionFoundation

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