Logical Reasoning Essentials: Strengthen Questions & Argument Structure

Operation Family: Strengthen Questions
  • Answer choice, if true, acts on the stimulus (arrow: answer ➜ stimulus)
  • Typical tasks: strengthen, weaken, supply assumption, resolve paradox
  • Evaluate: "Does this statement perform the required operation on the stimulus?"
Example: Gem World Advertisement
  • Claim (conclusion): You can count on fair diamond prices at Gem World
  • Evidence: Diamonds are “certified in writing”
  • Weakness: Nothing said about who certifies; could be same biased seller
  • Strengthening approach: Show certification is independent & unbiased, unlike other stores
Propositions vs. Sentences
  • Proposition = declarative unit that is true or false
  • e.g. "The sky is purple" (truth-apt)
  • Words/phrases alone ("purple snow") are not propositions
  • Sentence may contain one or more propositions, explicit or implicit
  • Complex wording can hide simple propositions; must extract them
Arguments: Premises & Conclusion
  • Argument = set of propositions where premises support a conclusion
  • Premise: A proposition that provides evidence, reasons, or support for the conclusion.
  • Conclusion: The proposition that is asserted to be true on the basis of the premises; what the argument aims to prove.
  • Diagram:
    • Premises written above a horizontal line
    • Conclusion below, preceded by ∴\therefore (three-dot "therefore")
  • LSAT often disguises structure by:
    • Re-ordering statements
    • Embedding references ("those people are wrong" → means conclusion "Pizza is delicious")
Identifying Conclusions & Premises
  • Focus on support relationship: which statement is supported, which support
  • Translate referential phrases ("wrong/mistaken") into the actual claim
  • Constant mental sorting is essential; speed without structure leads to errors
Indicator Words
  • Conclusion indicators: thus, therefore, hence, so, as a result, consequently, it follows that, accordingly, clearly
  • Premise indicators: since, because, for, after all, given that
  • Placement can flip (premise first or last); meaning > order
  • Use indicators as "handles" but do not rely on them exclusively