Which statement is always true regardless of p and q?

Question image

Understand the Problem

The question is asking which logical statement is always true regardless of the truth values of variables p and q. It presents four options related to propositional logic.

Answer

The logical statement that is always true regardless of the values of $p$ and $q$ is $p \lor \neg p$.
Answer for screen readers

The answer is $p \lor \neg p$.

Steps to Solve

  1. Identify the Statements List the logical statements provided in the question:

    • a. $p \lor \neg p$
    • b. $\neg p \to p$
    • c. $p \to q$
    • d. $p \land \neg p$
  2. Evaluate Each Statement Determine the truth value of each statement regardless of the truth values of $p$ and $q$.

  3. Analyze Statement a: $p \lor \neg p$ This is an example of the Law of Excluded Middle. It states that either $p$ is true or $\neg p$ (not $p$) is true.

    • Truth Table:
      $p$ $\neg p$ $p \lor \neg p$
      T F T
      F T T
    • Conclusion: Always true.
  4. Analyze Statement b: $\neg p \to p$ This represents a conditional statement. It's true unless $\neg p$ is true and $p$ is false.

    • Truth Table:
      $p$ $\neg p$ $\neg p \to p$
      T F T
      F T F
    • Conclusion: Not always true.
  5. Analyze Statement c: $p \to q$ This is also a conditional statement. It can be false if $p$ is true and $q$ is false.

    • Truth Table:
      $p$ $q$ $p \to q$
      T T T
      T F F
      F T T
      F F T
    • Conclusion: Not always true.
  6. Analyze Statement d: $p \land \neg p$ This is a contradiction because $p$ cannot be both true and false at the same time.

    • Truth Table:
      $p$ $\neg p$ $p \land \neg p$
      T F F
      F T F
    • Conclusion: Always false.
  7. Final Conclusion The statement that is always true regardless of the truth values of $p$ and $q$ is option a: $p \lor \neg p$.

The answer is $p \lor \neg p$.

More Information

The statement $p \lor \neg p$ illustrates the principle of the Law of Excluded Middle, a foundational concept in classical logic stating that a proposition must either be true or false. Therefore, it is always true.

Tips

  • Confusing the truth value of conditional statements, especially $\neg p \to p$, with that of disjunctions.
  • Misidentifying contradictions or tautologies without constructing a truth table.
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