Answer to Question #104692 in Discrete Mathematics for Martin

Question

QUESTION 2

Which of the following statements motivate the use of informal proof? Answer true or false to the
following informal proof statements:

a) Truth tables cannot demonstrate logical consequence for formulas containing more than 10
atoms.

b) Informal proof can sometimes explain why a logical consequence holds better than alternative
methods.

c) Not all connectives are truth functional, and hence truth tables do not capture the fully general
case of logical consequence.

d) Informal proofs contain no symbols and so can be understood by everyone.

Answer 1

With an informal proof, we might see compelling evidence that something is so but, at this level, it is possible that an exception exists somewhere.

So, the correct answer is c).