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The answer to Q1 is ``No." tex2html_wrap_inline138 is

displaymath148

Proof. tex2html_wrap_inline138 is true if and only if the mirror of tex2html_wrap_inline152 is not printable. But the mirror of tex2html_wrap_inline152 is tex2html_wrap_inline138 itself. Hence tex2html_wrap_inline138 is true iff it's not printable. By the definition of the biconditional, we thus have two possibilities: viz., either tex2html_wrap_inline138 is true and not printable, or tex2html_wrap_inline138 is printable and false. The second possibility violates one of the assumptions of the puzzle (viz., that tex2html_wrap_inline56 tex2html_wrap_inline58 never prints sentences that aren't true). So we are left with the other disjunct: tex2html_wrap_inline138 is true but not printable. QED

As to tex2html_wrap_inline144 , it must be false (since it's negation is true). Therefore by the hypotheses governing the puzzle this sentence is not printable. If we reinterpret `printable' as `provable' we can conclude that tex2html_wrap_inline144 is, as we say, undecidable, that is, neither it nor its negation is provable.



Selmer Bringsjord
Tue Jan 20 11:43:03 EST 1998