What is the name of the fallacy when one concludes P from P -> Q and Q?

Study for the Logical Reasoning STEM Test. Practice with flashcards and multiple-choice questions, each with hints and explanations. Prepare for success!

Multiple Choice

What is the name of the fallacy when one concludes P from P -> Q and Q?

From a conditional statement, if P implies Q, concluding P just because Q is true is a fallacy called affirming the consequent. The key idea is that Q can arise from causes other than P, so Q by itself doesn’t guarantee that P happened. For example, if rain implies the street is wet, and the street is wet, you can’t conclude that it rained—you could have used a sprinkler or another cause. The valid way to get Q is from P (modust ponens), not by jumping from Q back to P. The other listed forms describe either a valid inference or different invalid patterns that don’t correctly justify deriving P from Q.

From a conditional statement, if P implies Q, concluding P just because Q is true is a fallacy called affirming the consequent. The key idea is that Q can arise from causes other than P, so Q by itself doesn’t guarantee that P happened. For example, if rain implies the street is wet, and the street is wet, you can’t conclude that it rained—you could have used a sprinkler or another cause. The valid way to get Q is from P (modust ponens), not by jumping from Q back to P. The other listed forms describe either a valid inference or different invalid patterns that don’t correctly justify deriving P from Q.

More practice questions