[Agda] A philosophical question on absurd.

Thorsten Altenkirch Thorsten.Altenkirch at nottingham.ac.uk
Fri Aug 28 17:08:19 CEST 2020


The absurdity of absurd doesn’t only show up in the propositions-as-types explanation. Even purely logical the bottom elimination rule has the same counterintuitive property: ex falso quod libet, from false follows everything. The issue is rather linguistic in nature there isn’t really a counterpart to False in natural language. In my logic course I explained that False should be translated as “pigs can fly”. This also explains the definition of “not P” as “P -> False”. I used the following example: if a girl wants to say “I am not going to marry you”, she could say “If I am going to marry you then pigs can fly”. It means no. 😊

Thorsten

From: Agda <agda-bounces at lists.chalmers.se> on behalf of David Banas <capn.freako at gmail.com>
Date: Friday, 28 August 2020 at 14:12
To: Agda mailing list <agda at lists.chalmers.se>
Subject: [Agda] A philosophical question on absurd.

Hi all,

I'm brand new to Agda and the Curry-Howard isomorphism (and really loving this new exploration of both!), and I have a philosophical objection to how the absurd function is used to generate whatever we need to complete a proof.

I understand how we are able to satisfy the Agda compiler with the definition of absurd; my objection isn't mechanical/technical.

What bothers me is a feeling that I'm "cheating" when I use this function that can never be called, in order to "produce" that which I need to complete my proof.

I wonder if someone could offer a different perspective on this, for consideration.

Thanks!
-db




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