random

[Nick Perkins]

> "Alex Martelli" <aleaxit at yahoo.com> wrote:
> |"Even given (a powerful army) I could not (defeat Napoleon)".
> |Do you read this as "having a powerful army IMPLIES I
> |cannot defeat Napoleon"?  This doesn't sound right to me.
> |Surely it's "NOT (having a powerful army IMPLIES I can
> |defeat Napoleon)"?
>

"Lulu of the Lotus-Eaters" <mertz at gnosis.cx> wrote in message
news:mailman.991581425.24043.python-list at python.org...
.. quanta and Laplacian fantasies..
.. implicature
.. interlocutor..
.. negative epistemic attitude..
.. material conditional..

Sounds neat, but I only know simple logic.
Here's my take on the difference:

P : Powerful army
D : Defeat Napoleon

A: (P implies (not D))
"Given a powerful army, I could not defeat Napolean"

B: (not (P implies D))
"Having a powerful army would not ensure that I could..."

truth table:
P  D   A:(P implies (not D))  B:(not (P implies D))
0  0          1                      0
0  1          1                      0
1  0          1                      1
1  1          0                      0

The difference is that statement A is true if P is false,
whereas statement B can only be true if P is true.
Therefore, statement B implies that P is false.

So the statement "NOT( (powerful army)implies(deafeat Napolean))"
itself implies that "I do not have a powerful army"
And the statement"Having a powerful army implies I could not defeat
Napolean"
says nothing about whether P (powerful army) is true"

Otherwise the two statements are the same.

Sorry if i am stating the obvious, I just wanted to
convince myself that these things are not so complicated.