Re: Ancient Premise

[Jim Diamond <jimd@LINFIELD.EDU>]

On Thu, 28 Oct 1999 09:28:02 -0500 Karl Trappe
<trappe@PHYSICS.UTEXAS.EDU> wrote:

> Does anyone know the resource for this ancient premise.  I learned it in a
> high school symbolic logic class.  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.
>
> When Sheila Tobias visited the University of Texas at Austin, and spoke on
> "They're not dumb, they're different", many of my colleagues looked for the
> false premise and never heard the message.  I'd like to revisit the context
> of the quote, as it may explain a lot of our social interactions (or lack
> thereof) as scientists.    Karl

I don't know the origin of the rule, but I seem to recall this form of
logic dates back to Leibniz. I'm not a professional philosopher, so I'm
relying on what I learned way back when.

The rule I learned from sentential logic (logic without quantifiers
like "there is at least one critter..." or "for all critters that ...")
is "A false premise guarantees a true proposition." This does not
mean that "A false premise guarantees a true conclusion." There is no
guarantee regarding the truth or falsehood of the conclusion in
conjunction with the premise.

In symbolic form, a premise A is joined with a conclusion B into a
proposition: if A, then B. One could work out the truth table based on
the rules of implication, but in sentential logic, the proposition is
equivalent to (.not.A).or.B . In this form, its easier to see that if A
is false, then the proposition (.not.A).or.B is true, regardless of the
truth value of B.

I agree with you that there are many possiblities for abuse of this
rule.

Regards,
Jim
----------------------
Jim Diamond         Chemistry Department  McMinnville, OR 97128
jimd@linfield.edu   Linfield College      (503)-434-2471