It gives me no pleasure to be right on this.
I mean if you have a passport then you already have an 'ID card', but I certainly don't want to take that out with me to prove my age.
> Could you explain what is so distasteful about ID cards?"
which is roughly how humans say "ID cards are okay" (P0)
> I mean if you have a passport then you already have an 'ID card', but I certainly don't want to take that out with me to prove my age.
which is roughly how humans say "We already collect information that would be on an ID card and store it against a passport" (P1) provided only for completeness because it is not used later
> "Could you please give me your real name "celticninja", your phone number, your address, your NI number -- oh, and you'll need to install this app on your phone which I promise will never be used to monitor your location, purchases, friends. Then I'll explain."
which is roughly how humans say "If (ID cards are okay) (P0 again) then (there should be no problem sharing that information with me, a stranger) (P2). But (there should be no problem sharing the information with me, a stranger) (P2 again) - is absurd"
Therefore, if all of these were logical, then indeed this is a valid proof that ID cards are not okay by reductio ad absurdum, a valid proof technique.
I suppose the gap in the argument is in the logical statement P0 => P2. If some chain of argument could provide P0 => P2 then this would indeed be a valid proof of the falsehood of P0 by reductio ad absurdum to P2 an absurd conclusion. Of course I wrote it out to illustrate, but it was obvious it was reductio ad absurdum.
It just strikes me as curious that someone would point that out. A bit like saying "syllogism" when someone makes a one-step logical conclusion, which is not something that humans usually post on web forums. Then again, if you say "Knowledge is power" someone will inevitably say "France is bacon" ;) so there's a bit of an ability to prompt things out of human beings that only has phatic purpose. Perhaps Latin, in particular, draws this out of someone but I'd think it odd if people went around saying "quod erat demonstrandum" in replies to someone who proved something.