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From: Louis Valence <lvalence@example.com>
Newsgroups: comp.programming
Subject: Re: Everything I say is false.
Date: Mon, 14 Oct 2019 11:40:34 -0300
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Richard Heathfield <rjh@cpax.org.uk> writes:

> On 11/10/2019 14:20, Louis Valence wrote:
>> Richard Heathfield <rjh@cpax.org.uk> writes:
>>
>>> On 09/10/2019 20:10, mikegonta@gmail.com wrote:
>>>> Everything I say is false.
>>>
>>> That's not true.
>>>
>>> But *some* things you say are false, and the above is an example.
>>
>> Fun with logic. :-)
>
> Indeed. Here's an age-worn and very familiar paradox (bear with me here):
>
> Side A:
> +------------------------------+
> + The sentence on the other    +
> + side of this card is true.   +
> +------------------------------+
>
> Side B:
> +------------------------------+
> + The sentence on the other    +
> + side of this card is false.  +
> +------------------------------+
>
> If you now turn the card on its side and inspect the edge with a
> powerful microscope, you will see the following words, carved in
> carbon atoms individually arranged by people with far too much time
> and equipment on their hands:
>
> +------------------------------+
> + Everything written on Side A +
> + and Side B is bloody stupid. +
> +------------------------------+
>
> Paradox resolved!

I'm slow, so bear with me.  Either A is true or false.  Assume it's
true.  Then B must be true.  But if B is true, A cannot be true.  Okay.
Then assume A is false.  Then B must be false.  If B is false, then A
must be true.  Contradiction.  So we can't satisfy both statements
together with either truth-value.  Alright.  I see it.

Here's perhaps my favorite version!

--8<---------------cut here---------------start------------->8---
What is the probability that you'll randomly answer this question and
get it right?  Check all answers that apply.

(a) 25% (b) 50% (c) 60% (d) 25%
--8<---------------cut here---------------end--------------->8---

I think this one is really interesting.