No cat is a dog — Syllogisms Aptitude Question
No cat is a dog: Statements: No cat is a dog. All dogs are pets. Conclusions: I. No cat is a pet. II. Answer and worked solution on CodeKairo.
- Topic: Syllogisms
- Section: Logical Reasoning
- Difficulty: Hard
- Time target: 105 seconds
Question
Statements:
- No cat is a dog.
- All dogs are pets.
Conclusions: I. No cat is a pet. II. Some pets are not cats.
Which conclusion follows?
Options
- Only I
- Only II
- Both
- Neither
Show the answer and the worked solution
Correct answer: B. Only II
Worked solution
- All dogs are pets and no dog is a cat, so those pets are not cats: II follows.
- Cats could still be pets themselves, so I does not follow.
Answer: Only II.
The idea
A 'some are not' conclusion is far safer than a 'no' conclusion. Ask whether a single drawing can break the stronger claim; if so, reject it.
Shortcut. Standard pattern: 'No A is B' + 'All B are C' gives 'Some C are not A' — some pets (the dogs) are not cats — and never 'No A is C'.
Common trap. "Only I" — carrying 'no cat is a dog' across to all pets; cats can be pets even though no cat is a dog.