Practice question · Numerical answer
Modus tollens, hypothetical syllogism, disjunctive syllogism and contraposition are all derived rules. How many additional arguments become provable once they are added to the basic system?
Hints
- Derived rules are proved FROM the basic rules.
- Anything provable with them was already provable without them.
Show the answer
0
Why
None. Derived rules are theorems of the basic system, so they add no power whatever, only brevity. That is exactly why they are safe to use freely.
Practise Proof Strategy
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