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jonathanichikawa / for-all-x

Open-source logic textbook in LaTeX by UBC philosophy professor Jonathan Ichikawa
Creative Commons Attribution 4.0 International
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clarification on universal introduction rule #23

Closed jonathanichikawa closed 1 year ago

jonathanichikawa commented 3 years ago

I think I need to make explicit that universal introduction has to replace all instances of the given name with the variable. I think. I want to think a bit more about it but I realized we need to rule out a derivation of forall x Rax from Raa, in cases where a is arbitrary. (Suppose we have forall x Rxx as a premise.)

jonathanichikawa commented 1 year ago

I corrected this issue.