Re: An argument against modus ponens

george wrote:
On Sep 21, 8:52 am, John Jones <jonescard...@xxxxxxx> wrote:
Then kindly follow your own example and remember that we are talking
about formal languages. Unlike our natural language conditions, formal
languages do not have access to local weather forecasts.

But they DO have truth-values, both presumptively and potentially.

So the conditions in which a formal language is expressed enables it to have access to possible weather conditions.

They just do. It's just a fact about logic.

No. It's a fact about natural languages.

Logic is about what
happens
when you PRESUME that the truth of some sentence could somehow be
linked to the truth of another. That's just WHAT YOU ARE DOING
whenever
you are doing logic.

There are no presumptions in logic. P says no more than P. There's no presumption of R or not-P.

But that's not the point. The point IS, since
I HAVE
TWO DEGREES IN LOGIC AND YOU HAVE ZERO,

Sorry I missed the end of term barbecue. I'm veggie.

why are you trying to TELL
me what is going on? Why don't you just ASK??

I don't need to ask where I can see clearly.

Nobody ever said anything could BE different things.
Things can only be what they are.
Thankyou. Things can only be what they are, without truth or falsehood.

Oh, bull***. That is like saying you could be who and what you are
without a height or a weight.

Logic is not dependent on material contingencies.

These things INHERENTLY HAVE this
property
(of being boolean/bivalent in type).

No they don't. These things do not, cannot, have this property of bivalency. I've said why, but you just keep burping off beer and beefburgers.

So you can't speak of P being false.

I CAN SO TOO. I just DO.

Why? Because a false P assumes both P and R.

I truly don't know what you mean by R.

If P is false then another thing must take its place. If P 'it's raining' is false, then R 'its not raining'.

I think you are confusing P (the variable) with P (the sentence,
asserting
that the variable's value is true). I concede that there is some
ambiguity
of notation in the usual presentation around this.

WE are NOT talking about
words in the natural-language sense, OR about the things those words
refer to. WE ARE TALKING ABOUT *STRINGS*.
We are talking about SYMBOLS.
We are talking about FINITE LISTS OF CHARACTERS.
THOSE are our atomic building-blocks around here.
Then follow your own example and remember that. Strings etc represent
themselves. They don't tell us what the weather might be doing, whether
'it's raining' is false or not.

They do IF WE SAY they do.

Then for 'if P' you have to include R.

"Dog" IS A STRING, dumbass.
You can't claim that it doesn't MEAN a certain kind of 4-legged
carnivorous
mammal IF WE'RE SPEAKING ENGLISH.

I can if you say 'dog' is just a string. There are no implicit differences between strings.

These strings OCCUR IN A CONTEXT
that IMPUTES meaning to them.
When the context is logic, some of the strings are propostions and
some of them
are sentences, and formally, SENTENCES HAVE truth-values, JUST as
surely
has they have letters. Those are a DEFINED PART of what it MEANS to
BE a sentence.

Logic can borrow scenario's or contexts from natural language, but when it does so it can't use the same syntax it does for a syntax-only logic. P says P. But in the non-syntactical logic of 'if P' we must say P and R.

The number is not (necessarily) the SAME as its numeral, and the
truth-
value is not the same as the symbol or string that names it, BUT THEY
MIGHT AS WELL be; they are both abstract.
That is airy-fairy land.

Of course it is! That is WHAT THIS IS ALL ABOUT!

I'm surprised you've gone there.

That's why you can't do logic.
You have no conception of the realm where it is occurring
(well, you do; we all do; it's unavoidable, but you are arguing
against
it because you are a dip***).

You continually appeal to an absolutist, truth conferring property of a transcendent logic. That is, you seem to think that all we have to do is state something in logic and it becomes truth.

> Peter Pan says
that numbers are numerals when they're abstract.

No, we ALL notice that numerals, LIKE numbers, are abstract.
That doesn't MAKE them numbers; it doesn't make the distinction
disappear.

That's sad. It's sad that someone out there thinks that numerals and
numbers are all alike in the far-off, auto-put-right land of
mathmatico-logic.

That's obviously THE ONLY place THEY CAN be.

There's that 'everything's is put right' property of logic again. That's an old silly belief.
.