11 May
2011
11 May
'11
9:16 p.m.
Adam Goucher's sentence "If 3 is a prime, then the contrapositive of this sentence is false" and its formal contrapositive "If the contrapositive of this sentence is true, then 3 is not prime" may contradict one another, but what I want is a provably true sentence whose formal contrapositive is provably false. Jim Propp