ASome birds can swim. Penguins are birds. Therefore, all penguins can swim.
BAll cats are animals. Whiskers is a cat. Therefore, Whiskers is an animal.
CIf it rains, the ground is wet. The ground is wet. Therefore, it rained.
DMost students passed. Jamie is a student. Therefore, Jamie passed.
Option B follows the structure: All A are B; X is A; therefore X is B. This is valid — if both premises are true, the conclusion must be true. Option A jumps from 'some' to 'all.' Option C affirms the consequent (the ground could be wet from a sprinkler). Option D uses 'most,' which does not guarantee the conclusion for any specific individual.
Question 2 True / False
A valid argument with false premises usually produces a false conclusion.
TTrue
FFalse
Answer: False
Validity guarantees that IF the premises are true, the conclusion is true. But when the premises are false, the conclusion can be either true or false — validity makes no promise either way. 'All prime numbers are even. 4 is prime. Therefore 4 is even.' Both premises are false, but the conclusion happens to be true. The argument is valid (the structure is correct) but not sound.
Question 3 Short Answer
Explain the difference between validity and soundness, and give an example of a valid but unsound argument.
Think about your answer, then reveal below.
Model answer: A valid argument has a structure where the conclusion must follow from the premises. A sound argument is valid AND has all true premises. Example: 'All reptiles can fly. Snakes are reptiles. Therefore snakes can fly.' The structure is valid (All A are B; X is A; so X is B), but the first premise is false, making the argument unsound.
Soundness is the higher standard — it requires both correct logical structure (validity) and factual accuracy of premises. You can verify validity by checking the argument's form alone, but soundness requires also checking whether the premises are true in the real world.