User:Vvv1209/sandbox

Wason’s logic puzzle asks the following question: ''You are shown a set of four cards placed on a table, each of which has a number on one side and a letter on the other side. The visible faces of the cards show A, B, 4 and 7. Which card(s) should you turn over in order to test the truth of the following rule: “if a card shows a vowel on one face, then its opposite face shows an even number.”''

Solution
The correct response is to turn the cards showing A and 7, but no other card. Remember how the proposition was stated: "if a card shows a vowel on one face, then its opposite face shows an even number." If we turn over the card labeled "A" and find that it is odd, this invalidates the rule. Likewise, if we turn over the card labeled “7” and find that it has a vowel on the other side, we invalidate the rule. On the other hand, we cannot invalidate the rule if we turn over B or 4.