Re: ex falso quodlibet

[John Denker <jsd@MONMOUTH.COM>]

At 09:28 AM 10/28/99 -0500, Karl Trappe wrote:
> Does anyone know the resource for this ancient premise.

The ancient expression is
 * ex falso quodlibet
which means, quite literally, "from falshood, anything you like".

I've also seen it called
 * "FA" for False Antecedent.
 * The Absurdity Rule

For a reference, you can try e.g.
  http://philosophy.ohio-state.edu/tennant_absurdity_rule.html

> I learned it in a high school symbolic logic class.

Good.

> I have also observed the side effects of
> starting with it as an assumption in dealings between co-workers, ie,
> looking for the false premise in order to disagree with all which followed.
> I found that to be very damaging to constructive interactions, or even to
> just *hearing* the other person.

That seems like quite a leap.

If the other person is offering proofs and syllogisms based on a
self-contradictory premise, then you *should* reject everything that
follows.  _Ex falso quodlibet_ is not an assumption -- it's a theorem of logic.

On the other hand, syllogistic inference is not the only type of inference
in the world.  Almost all of our every-day inferences are based on an
accumulation of imperfect data.  Rarely is a single assertion strong enough
to prove the conclusion, nor strong enough to contradict assertion
precisely enough to create a contradiction that justifies application of
_ex falso quodlibet_.

The statement "suppose we escape from inside the event horizon" is unusual
because it achieves a very high level of self-contradiction.


______________________________________________________________
copyright (C) 1999 John S. Denker             jsd@monmouth.com