Re: Modal logic

Hello xuqiuhua,

The area of modal logic is quite rich in its application. It is not
just for epistemology. Its usages are panoramic with styles to teach
critical thinking, law, rhetoric, hypotheses formulations for science
and ways to analyze physics, math, biology and economics.

Some people think that it is about simple if/then, but if/then is very
complex.

What I am about to give you is not standard.

Let us begin with if/then.

It is a subjunctive indicative. It maps the movement from the possible
to the actual with 'then' as the boundary marker.

It is unidirectional. Time flows always in one direction with p
rigidly designated as the antecedent and q rigidly designated as the
consequent. If you reverse, it just means you are moving from a
possible consequent to a certain antecedent. It will be like thinking
backwards.

For example, 'if John asked Mary (possible antecedent) then they made
love (certainty of consequent.

Reverse: 'if they made love (possible consequent) then John asked Mary
(certainty of antecedent.) Here you are just reasoning backwards. The
structure and order of events is still moving forwards, otherwise you
will have rape.

It is paradoxical. 'If someone drinks then everyone drinks.' This
means that there is another someone who is not drinking, thereby
negating the beginning conditional for everyone to drink. Its
structure is like 'I am lying.' It is like (A & Drinks) + (A & ~
Drinks) --> Everyone & Drinks. This would lead to algebraic
cancellation. There are ways out of this paradox, but it is
complicated.

There are also two ways to analyze the possible worlds' semantics.

The first is Russell.

'If there is a present King of France then he has balls.'

This is what I call actual worlds' probability space states.

Russell was trying to look for ways to retain the rule of the excluded
middle and to avoid a null hypothesis. This is because the
undetermined in 1905 is considered metaphysical.

Russell was a strict empiricist.

If you look at the sentence and turned it to its negation, 'If there
is a present King of France then he has balls,' or 'if there is a
present King of France then he has **no balls,** (constitutional
monarchy) neither one will hold truth validity, since there is no
actual present day King of France sitting on the throne. There is no
true or false.

The way to test truth validity here is to see if there is an actual
present King of France sitting on the throne. If there is no actual
physical person, then the rigid designator, 'the present King of
France' is false, and whatever flows from the sentence, that he 'has
balls', is also false.

However, you can also analyze it another way. It is my reevaluation of
Strawson.

He looked straight into the meaning of the sentence and what it
referred to.

Meaning to him is not always about the sentence pointing to an actual
world.

For example, in world I, 'if there is a present King of France then he
has balls.'

In world II 'if there is a present King of France then he has no
balls.'

In either of these hypothetical worlds, you can empirically test truth
validity by analyzing to see which world is true and which world is
false.

But if there is no present King of France at all to speak of, then it
is a null hypothesis.

It is not in Russell's case false.

In some instance, this is not metaphysical. Some people are duped into
thinking that way due to the label of 'possible worlds' semantics.

But if you think about it, this is how probability logicians and
statisticians think.

We might be referring this sentence not to an actual physical King of
France, but a past one. If this is the case then we can test the truth
validity of whether he has balls or not.

Note: This is historical analysis of possible worlds' semantics. It is
not anything metaphysical.

If it is speculative, it means we are opened to the possibility that
someday the French will elect for themselves a possible King of
France. If that is the case, then he should also have balls or no
balls. ;-)

In possible worlds' semantics, there is an entirely new way of looking
at modal logic in terms of the counterfactual. It is had/then/would.

The null hypothesis in this world is different from the regular if/
then.

Here, you have entered into a brave new world of exciting
possibilities and research.

But it is far too complex.

B.T.

On May 2, 11:20 pm, xuqiu...@xxxxxxxx wrote:
I am studying modal logic by myself. The textbook I use is Modal logic
writen by Blackburn et al. I want to find several partners to discuss.
My email and msn is: xuqiuhua...@xxxxxxxxxxx, if you have the same
interesting please inform me. I am looking forward for your
participation.


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