Is "logic" the new word of the decade?

[Revoltingest]

Look up tautology. All logic is in the brain and only true in the brain as valid.

Here is a valid deductions.

P1: All birds can fly.
P2: Penguins are birds.
C: Penguins can fly.

This deduction is valid, but not sound. If you don't understand that as the limit of logic, then that is not my problem.

Results of logic are only as valid as the premises.

All Scots are Popes.
Revoltingest is Scottish.
Therefore, Revoltingest is Pope.

 

[Sunstone]

Ahh, that helps sort things out in my mind

I see you grasp the thrust of my argument, and have mastered the ins and outs of it.

 

[mikkel_the_dane]

Results of logic are only as valid as the premises.

All Scots are Popes.
Revoltingest is Scottish.
Therefore, Revoltingest is Pope.

No, you mean sound. Check out valid versus sound in logic.

 

[Unveiled Artist]

Logical can mean sound reasoning, it could mean this makes sense.

By definition it means

of or according to the rules of logic or formal argument.

Whether it be about the existence of god or talking about how the earth goes around the sun, each has a set of rules whether tradition or physics and when those rules are followed it's said to be logical.

As for the study of logic that's completely separate than just using the word logic as another word for reasoning.

Another definition.

capable of reasoning or of using reason in an orderly cogent fashion

It's best to go off the context of the OPs. If you use one definition for all OPs that use a said word, it won't make sense (it won't be logical). Just as the word god is different for each person. You have to go by the term and definition that's used in the OPs in their given context or you'd be arguing about how people don't use the "right" definition when there are multiple.

I believe has nothing to do with this.

 

[Thief]

hey....btw

deduction moves from general observations to a specific notion
induction moves to the general application

one worker succeeds to get it done.....therefore we can hire anyone to do the same

false

 

[Revoltingest]

No, you mean sound. Check out valid versus sound in logic.

I meant exactly what I posted.

 

[Polymath257]

Usually, logic refers to abiding by patterns of reasoning that can justify a position based on previously agreed upon positions.

Aristotle famously wrote down several laws of logic (non-contradiction, no middle third, etc), but he was quite far from giving a complete list of such laws.

Formal logic began much later with Boole, who did boolean logic. This is, in essence, what is known as propositional logic. it deals with words such as 'and', 'or', 'if...then..', 'not', 'if and only if'.

But Boolean logic doesn't deal with another couple of important phrases, 'there exists', and 'for every'. Adding these to the analysis leads to what is known as prepositional or quantifier logic.

There is yet another type, more controversial, known as modal logic, which deals with 'possible worlds'. So 'possible' and 'necessary' are key words for this type of logic. Unfortunately, while the basic rules for propositional and quantifier logic are agreed to and very clear, those for modal logic are debated still.

Then we get into the logic of equality and of collections of objects. This leads to modern mathematics, which is ultimately based on set theory. Here, the basic assumptions are generally agree upon, but it is KNOWN that they cannot be complete (even when limited to math).

Then, there are the non-standard logics. Three valued logic, paraconsistent logic, logics without the law of excluded middle, etc. All are *internally* consistent, but they can give very different results than classical logic. Fuzzy logic is a type of non-standard logic where, in essence, we assign probabilities to truth or falsity. Quantum logic is yet another variant.

One aspect is that NONE of these necessarily say anything about the real world. They ALL say how to go from one set of assumptions to conclusions based on those assumptions. But they do NOT say how to arrive at the original assumptions.

Questions concerning causality, time, matter, etc are NOT ultimately questions of logic. Something beyond logic is required for the assumptions upon which logic can work. This is the case for the rest of metaphysics as well.

Without assumptions that all can agree to, logic alone can go nowhere.

 

[mikkel_the_dane]

I meant exactly what I posted.

Yeah:
"A deductive argument is said to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. A deductive argument is sound if and only if it is both valid, and all of its premises are actually true. ..."
Validity and Soundness | Internet Encyclopedia of Philosophy

 

[mikkel_the_dane]

...
One aspect is that NONE of these necessarily say anything about the real world. They ALL say how to go from one set of assumptions to conclusions based on those assumptions. But they do NOT say how to arrive at the original assumptions.

Questions concerning causality, time, matter, etc are NOT ultimately questions of logic. Something beyond logic is required for the assumptions upon which logic can work. This is the case for the rest of metaphysics as well.

Without assumptions that all can agree to, logic alone can go nowhere.

Yeah.
But we don't need assumptions that all can agree to, because agreement is subjective.

 

[Revoltingest]

Yeah:
"A deductive argument is said to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. A deductive argument is sound if and only if it is both valid, and all of its premises are actually true. ..."
Validity and Soundness | Internet Encyclopedia of Philosophy

So....?

 

[mikkel_the_dane]

So....?

My deduction was valid, but not sound. Read the words and use your brain.

 

[Secret Chief]

-a particular way of thinking, especially one that is reasonable and based on good judgment.

The problem is the word "good". It has no objective referent and is without evidence.

- a way of thinking about something that seems correct and reasonable, or a set of sensible reasons for doing something.

Again correct, reasonable and sensible have no objective referents and is without evidence.

Sure but I only quoted from dictionairies, I don't write them

 

[Revoltingest]

My deduction was valid, but not sound. Read the words and use your brain.

It seems you're objecting to my post.
But not giving reasons that make sense.

 

[Polymath257]

Yeah.
But we don't need assumptions that all can agree to, because agreement is subjective.

Then the conclusion follows.

 

[mikkel_the_dane]

It seems you're objecting to my post.
But not giving reasons that make sense.

Sense is not logic as such.
So again. You conflate truth, valid and sound.
Validity and Soundness | Internet Encyclopedia of Philosophy
A deductive argument is said to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. A deductive argument is sound if and only if it is both valid, and all of its premises are actually true. ...

 

[Revoltingest]

Sense is not logic as such.

Never claimed it is.
It seems that a lot of claims I've not made are in dispute.

 

[Sunstone]

I've heard it put this way: Logic is like the rules of a game, which is different from saying logic is the game itself. I haven't thought that through yet, but it looks good enough offhand.

 

[Secret Chief]

That's the best I can recall the distinction ever being laid out. Only I believe the Western tradition of studying logic as a distinct subject began with the ancient Greeks, long before the invention and rise of analytic philosophy. But perhaps I've misunderstood what you meant by 'analytic philosophy'?

We're on the same page. I think Western analytic philosophy is indeed the modern extension of the Ancient Greeks. It is called "analytic philosophy" to distinguish it from "Continental* philosophy" - the likes of Nietzsche and Kierkegaard.

(*stupid term, the same as "Tibetan Buddhism" is)

 

[mikkel_the_dane]

We're on the same page. I think Western analytic philosophy is indeed the modern extension of the Ancient Greeks. It is called "analytic philosophy" to distinguish it from "Continental* philosophy" - the likes of Nietzsche and Kierkegaard.

(*stupid term, the same as "Tibetan Buddhism" is)

There is more to it than that.

 

[Polymath257]

I've heard it put this way: Logic is like the rules of a game, which is different from saying logic is the game itself. I haven't thought that through yet, but it looks good enough offhand.

I think of logic as the rules of moving the pieces in chess. This is *part* of the game.

But the initial set up is a very important aspect as well. Who moves first is as well. If you change the initial placement of pieces, that would drastically change the game of chess (possibly even trivializing it).