Erwin Schrödinger’s Birthday

[O'Searcaigh]

If that that is 'is' is that that is not 'not is', is that that is 'not is' that that is not 'is'?

Formally (syntactically) yes, whether the meaning of 'is' is an is of attribution (material implication) or is an is of identity (bi-conditional) because “that that is 'is' is that that is not 'not is' if and only if that that is 'not is' is that that is not 'is'” -- otherwise known as the “Law of Transposition.” However, informally (semantically) it all depends on what the meanings of all the is’s are and especially if the ‘is not’ is an is not of specific denial or an is not of nothingness and hence semantically open to a fallacy of ambiguity (equivocation). At least that’s my take on it as a student of nothing!