Practice question · True or false
Natural deduction is strictly weaker than truth tables: some valid arguments cannot be proved in it.
Hints
- This concerns the completeness of the system.
- Completeness says every valid argument HAS a proof, which contradicts the claim.
Show the answer
False
Why
False, the system is complete, so every valid argument has a proof, and sound, so nothing invalid does. The two methods agree exactly; natural deduction trades exhaustive checking for rule-following, not power.
Practise Natural Deduction: The Rules
The app has 3 more questions on this lesson, and keeps your place in the course. Philosophy I is free to start.
More questions on Natural Deduction: The Rules
- Arrange the steps of a conditional introduction proof in order.
- Why may a line from a closed subproof not be used later in the proof?
- A proof of "if P then Q" by conditional introduction requires how many assumptions to be made and then…
- Which statements about natural deduction are correct?
- Truth tables establish validity by surveying every valuation, whereas natural deduction constructs a…
- Match each proof technique to the shape of reasoning it formalises.
- Sort each rule by whether it introduces or eliminates a connective.