With the Liar
Statement—i.e. “This statement is false,” which we can translate as “p = this
statement (p) is false = (p = ~p)”— the definition
of p is false, not p itself. What does it mean for a definition to be false? It
means that it is formally invalid. This in turn
means that it is not permitted within our logic to use a definition of this
form. Note that the statement of a definition implies the statement that it defines, but it is not identical to the statement it defines.
I.e. Def. p > (p = -p).
Def. q > ( q = -q) S
Def. q S
q = -q MP
q S
-q ES
q & -q CONJ
-q IP
q ES
q & -q CONJ
-(Def. q) IP
(Def. q > (q = -q)) > -(Def. q) CP
∀p [(Def. p > (p = -p)) > -(Def. p)] UG
(1), QED
In any case, the above proves that the Liar Statement is falsidical and not a real antinomic paradox.
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