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Shouldn't this question fail at the parsing stage then, before it has even been asked? Q: All stonemen are ... A: ERROR: Undefined operation. Stonemen do

• Jtsummers 3y ago
  That's certainly one option. In a way, that's what the colloquial understanding of the expression would entail. In colloquial use if you were to say, "All unicorns are blue" no one can meaningfully contradict nor confirm the statement, the statement is neither true nor false because there are no unicorns (this all assumes we're not discussing in a context where unicorns "exist", like about a particular fantasy setting or animated series). In syllogistic logic it becomes false because of the foundation of that logic (centered on reality, what exists and can be defined, not on fiction). Nothing true can be said about all of some non-existent thing because, well, it doesn't exist, so the statement must be false. In modern predicate logic it's considered true, because even though there are no unicorns we (someone) decided that it should be true by convention when the set is empty (turns out to have useful properties if we permit this). These are just the rules that we've used for our logic, a choice we made. We're generally, in programming, operating under the modern logical rules, using neither colloquial rules nor syllogistic rules, so our programs are consistent with that last interpretation.