Question

A duck named Donald Duck says "All ducks always lie." Based only on the information above, which one of the following statements can be logically inferred with certainty?

• A. Donald Duck always lies.
• B. Donald Duck always tells the truth.
• C. Donald Duck's statement is true.
• D. Donald Duck's statement is false.

Hint:

Whenever a universal self-referential claim leads to a contradiction, the safe logical inference is that the statement itself is false.

Answer 1

The Correct Option is D

Step 1: Analyze the statement.
Donald Duck says, "All ducks always lie." This is a universal claim, meaning if it were true, then every duck (including Donald Duck himself) would always lie.

Step 2: Check for contradiction.
If Donald is lying (as per his own statement), then not all ducks always lie — which means his statement cannot be true.

Step 3: Logical inference.
The statement "All ducks always lie" creates a paradox because if it is true, Donald Duck must be lying, but if he is lying, then the statement cannot be universally true. Therefore, the only logical certainty is that Donald Duck's statement is false.
\[ \boxed{\text{Donald Duck's statement is false.}} \]