Proof of logic

[RandFan]

Actually, some sceptics do say: "There is no god".

I think Dawkins says it best. There is a possibility that there is a god. It is so unlikely though that we can say there is no god just as easily as we can say there is no teapot orbiting the sun (independent of earth that is).

But, you are correct, what they actually mean is something like: "At this time, we have found no evidence of god that doesn't have another, simpler, explanation. This could change when new evidence appears."

No. That's not right. There is no evidence. Period. End of story. Full stop.

 

[Beerina]

Actually, some sceptics do say: "There is no god".

Guilty!

But, you are correct, what they actually mean is something like: "At this time, we have found no evidence of god that doesn't have another, simpler, explanation. This could change when new evidence appears."

Yes, which often yields a pithy response along the line of, "At this time, we have found no evidence of unicorns, fairies, or of teapots in orbit around Betelgeuse that doesn't have another, simpler explanation. This could change when new evidence appears."

If this universe isn't what it seems to be, then I think it would be far more likely it's a virtual reality (so to speak, could be "real" in the sense that wood is really out there) created by advanced creatures for one of innumerable reasons.

 

[BillyJoe]

I think Dawkins says it best. There is a possibility that there is a god. It is so unlikely though that we can say there is no god just as easily as we can say there is no teapot orbiting the sun (independent of earth that is).

No. That's not right. There is no evidence. Period. End of story. Full stop.

RandFan, I mostly agree with Dawkins.
I used the words "something like" and then quoted streamlet's post. So I wasn't meaning to go along with that post completely. I actually go with Dawkins when he says that it is highly unlikely that there is a god. I disagree, as you know, that god, in this respect, is the same as the tooth faerie (for a clearer example). And I disagree that it is okay to say "there is no god", when what you actually mean is that "it is highly unlikely that there is a god".
But, anyway, we have had that argument.

 

[RandFan]

RandFan, I mostly agree with Dawkins.
I used the words "something like" and then quoted streamlet's post. So I wasn't meaning to go along with that post completely. I actually go with Dawkins when he says that it is highly unlikely that there is a god. I disagree, as you know, that god, in this respect, is the same as the tooth faerie (for a clearer example). And I disagree that it is okay to say "there is no god", when what you actually mean is that "it is highly unlikely that there is a god".
But, anyway, we have had that argument.

Yes, I agree we have. We will simply disagree.

Thanks,

RandFan

 

[blobru]

Actually, I am much less sophisticated than that.

If you cannot prove logic, then how can you be so sure of it that you disprove god with it?

Any sufficiently advanced system of logic will generate truths that can't be evaluated within the system; you need something (or someone) outside the system for that. So there are logics which can't prove themselves, but you can always invent a bigger logic that does prove the smaller one, and then an even bigger one, and so on... in theory until you get enough power to 'prove' or 'disprove' God (assuming everyone agrees with your axioms -- good luck with that!) However, the basic point is if God is meaningful, then whatever meaning you give It involves logic; if you want to talk about "God", you need logic; if not, then you're left with a meaningless God that you can never talk about, except to say It's "meaningless", "unknowable", "transcendent", or whatever?

 

[Darth Rotor]

Can you prove the rules of logic somehow?

If there is no proof for logic, how can one be so sure in it?

Can you prove a hammer somehow?

Logic, and the rules of logic, are tools suitable for some tasks. A hammer is a tool suitable for some tasks. Math is a tool used in many fields of endeavor, and math uses the tool of logic for many of its most useful tools in the Great Big Tool Box of mental task accomplishment. (Igor Sikorsky used that, among other tools, to invent useful things like helicopters.)

Note: Complexity, thanks for the lovely summary about statements and other fundamental matters.

JetLeg:

What interest do you have in proving a hammer?

"If there is no proof for a hammer, how can one be so sure in it?"

Do you know how nonsensical that question is?

DR

 

[JetLeg]

No, you can see a hammer, you cannot see logic.

 

[JetLeg]

Any sufficiently advanced system of logic will generate truths that can't be evaluated within the system; you need something (or someone) outside the system for that. So there are logics which can't prove themselves, but you can always invent a bigger logic that does prove the smaller one, and then an even bigger one, and so on... in theory until you get enough power to 'prove' or 'disprove' God (assuming everyone agrees with your axioms -- good luck with that!) However, the basic point is if God is meaningful, then whatever meaning you give It involves logic; if you want to talk about "God", you need logic; if not, then you're left with a meaningless God that you can never talk about, except to say It's "meaningless", "unknowable", "transcendent", or whatever?

I am not that sure that if you are talking about meaning and definition, you are presupposing logic. Why?

 

[cyborg]

No, you can see a hammer, you cannot see logic.

How do you think you see a hammer then? It simlpy 'happens'?

 

[blobru]

I am not that sure that if you are talking about meaning and definition, you are presupposing logic. Why?

Logic is the study of statement and implication. Every definition is a statement: "Green is a color"; "Gravity is a force"; "God is great"; etc. So any statement, to have precise meaning, presupposes logic.

Aristotle's logic starts by defining "definition":
A is A (once you name some thing, then the name refers to that thing).
A is B or not-B (a thing either has a quality or it doesn't. If it does, that quality is part of its definition).
A is not B and not-B (sort of the same deal as above -- qualities themselves must be well-defined).

Seems a fair minimum for any "definition": so any proper definition is bound by logic, open to discussion and criticism.
Of course, there are plenty of non-logical statements that have "meaning" as well, but not precise meaning. Metaphorical statements can take on many meanings; for example -- "God is the first light of the evening star and the last light of the morning star"; "God is the bird's song in spring and the bird's flight in autumn"; "God is the hole in the donut and the swirl in the cocoa", etc. -- which may or may not "mean" any number of things to anyone; fun perhaps, suggestive, but certainly not well-defined. (Mind you this is how mystics talk about God; as long as you stick to metaphor, logic can't get you. But if you want your God to justify anything, like a system of ethics say, you need more than metaphor, which only offers images, not axioms).

Anyway, a bit long-winded, sorry! but that's why, I think.

 

[Darth Rotor]

No, you can see a hammer, you cannot see logic.

But I can see reason, and I also know a fool when I see one.

DR

 

[slingblade]

I can't see air. Air must not exist.

I can't see fear. It must not exist.

I can't see love, or time, or nothingness. Those things don't exist.

Above all, I can't see JetLeg (whatever the hell a jet leg is) so I know it doesn't exist.

 

[JetLeg]

But it all ends up with logic being just a premise which you take. What if this premise is wrong?

 

[cyborg]

What if this premise is wrong?

Logic cannot be 'wrong'. It merely has rules and consequences of those rules.

'Wrongness' requires something against which to decide the validity of a particular logic.

 

[Mangafranga]

Logic cannot be 'wrong'. It merely has rules and consequences of those rules.

'Wrongness' requires something against which to decide the validity of a particular logic.

So a logic which allows "If p then q, q, so p" is not wrong then?

 

[cyborg]

So a logic which allows "If p then q, q, so p" is not wrong then?

Again, determining whether or not that logic is wrong is contingent on some qualification to compare it against.

 

[Mangafranga]

Again, determining whether or not that logic is wrong is contingent on some qualification to compare it against.

What is wrong with comparing it the world? This argument holds by that logic-

If I am writing the talk I will be giving in a few days then I am be typing on the keyboard
I am typing on the keyboard
So I am writing the talk I will be giving in a few days

The premises are true, the conclusion is false. Does this not indicate a deficient logic?

 

[cyborg]

What is wrong with comparing it the world?

Did I say anything was 'wrong' about it? I just said you need something to compare a logic against in order to determine it's 'validity' - that is the validity of a logic is rather dependent on what you want it to do.

The premises are true, the conclusion is false. Does this not indicate a deficient logic?

If the validity of your logic requires that 'true' premises lead to 'true' conclusions then yes - but you should remember that 'true' and 'false' are just descriptors for an outcome of a logical process; do not equate them to 'right' and 'wrong'.

 

[Mangafranga]

Did I say anything was 'wrong' about it? I just said you need something to compare a logic against in order to determine it's 'validity' - that is the validity of a logic is rather dependent on what you want it to do.

If the validity of your logic requires that 'true' premises lead to 'true' conclusions then yes - but you should remember that 'true' and 'false' are just descriptors for an outcome of a logical process; do not equate them to 'right' and 'wrong'.

I didn't get the memo where we totally removed the semantics and the study of arguments from logic. So I will just state what I want from my logic.

I want my logic to formalize correct arguments. I would contend that the argument form I presented is just plain incorrect.

 

[slingblade]

So a logic which allows "If p then q, q, so p" is not wrong then?

But logic doesn't "allow" that. This form is known as "affirming the consequent," and is an invalid form, a fallacy.

In words:
If it rains (p), then my car will be wet. (q)
My car is wet (q), therefore, it must have rained. (p)

One can immediately see the problem with this. There are other ways, besides rain, your car could get wet. Someone might have sprayed it with a hose, someone could have thrown a bucket of water, a street cleaner could have malfunctioned...other reasons.

But it's not that the logic is wrong; the logic shows you how the statement is invalid. Validity relates to form, soundness relates to content.

As was said before, by Darth, logic is but a tool one uses on words, statements, and arguments.