## How do we know our reasoning is valid?

Known unknowns and unknown unknowns!

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Greta
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### Re: How do we know our reasoning is valid?

Hobbes' Choice wrote:
Greta wrote:Relativity says that we can't know whether our reasoning is ultimately valid, only relatively so. We can't be sure of the reality of our foundation ideas. Dalek's idea of starting with your own consciousness makes sense, although that may be a perspective error.
Actually all analytical reasoning is fully self validated. For example because 1+1=2, 1-2=1 is 100% valid.
The trick is to not let yourself be drawn into a position that this says anything about the reality or the world around you.

You can use this to model reality. For example If I have two oranges and give one away I shall have one orange. However no orange is the same as any other and so this does not verify the analytical assumption.
Fair point. We can work out all many reliably practical, if sketchy, relativities but the foundation of those relative entities is a mystery, if a foundation exists.

wirius
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### Re: How do we know our reasoning is valid?

Hobbes' Choice wrote: Please state HOW this is an induction!
Repeating the assertion does not make it more truthful.
It would be easiest if you would read what I'm telling the OP to go check out. Go to"Subjective Deduction Part 4 and End" here on the forums if you want to get to the induction part. I would rather not rewrite a page or two worth of specifics here when its over there. viewtopic.php?f=17&t=19341

Greta, might want to check it out too. One of the goals of what I wrote was to establish a foundation that isn't sketchy. I'ld like to hear whether you think I succeeded or not.

Hobbes' Choice
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### Re: How do we know our reasoning is valid?

wirius wrote:
Hobbes' Choice wrote: Please state HOW this is an induction!
Repeating the assertion does not make it more truthful.
It would be easiest if you would read what I'm telling the OP to go check out. Go to"Subjective Deduction Part 4 and End" here on the forums if you want to get to the induction part. I would rather not rewrite a page or two worth of specifics here when its over there. viewtopic.php?f=17&t=19341

Greta, might want to check it out too. One of the goals of what I wrote was to establish a foundation that isn't sketchy. I'ld like to hear whether you think I succeeded or not.

Hot air Wirius. You don't know why you are calling it an induction because you do not know what it means - as I keep telling you.

wirius
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### Re: How do we know our reasoning is valid?

Hobbes' Choice wrote:

Hot air Wirius. You don't know why you are calling it an induction because you do not know what it means - as I keep telling you.
Page nine here. viewtopic.php?f=17&t=19283 If you don't remember, I posted exactly what induction was. Again, I have the links to show you exactly where I define induction, and make my point. I don't feel like writing all of that again. If you want to take the discussion back where we left off there, I'ld be more than happy to. Lets not derail the OP's thread here.

Hobbes' Choice
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### Re: How do we know our reasoning is valid?

wirius wrote:
Hobbes' Choice wrote:

Hot air Wirius. You don't know why you are calling it an induction because you do not know what it means - as I keep telling you.
Page nine here. viewtopic.php?f=17&t=19283 If you don't remember, I posted exactly what induction was. Again, I have the links to show you exactly where I define induction, and make my point. I don't feel like writing all of that again. If you want to take the discussion back where we left off there, I'ld be more than happy to. Lets not derail the OP's thread here.

Please state the "Brains in Vats" argument.

Necromancer
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### Re: How do we know our reasoning is valid?

Plausibility is a good measure for knowing when the reasoning is valid, IMO. It's also given that plausibility implies logical and mathematical truths. One arrives at plausibility by careful assessment.

One place to start: https://en.wikipedia.org/wiki/Plausible_reasoning

(I'm by the impression that the OP doesn't ask for simple validity (of logics or mathematics etc.).)

sthitapragya
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### Re: How do we know our reasoning is valid?

UhOH wrote:Recently I have been wracked by global scepticism, are we brains in vats, were the world and all our memories created last Thursday etc. I found that with the use of certain logical tools like Ockham's razor and abductive reasoning that I could dispel some of these sceptical doubts. But how do I know that my reasoning is true? How do I know that there isn't, say, a 100% probability that we are brains in vats? Couldn't I expand this to be more general as well, how do I know whether my deductive reasoning is valid? How do I know if any of my reasoning is true at all?
When you play a video game you will do everything not to die and become better at the game. You will basically try to thrive. There is no point to a game. It is just a game. You know this, yet you give your everything to survive and thrive. So even if you are a brain in a vat and your life is an illusion why would you want to see GAME OVER displayed on your screen?

If however life is real and you mistake it for an illusion. It will not be game over. You will really be dead.Why would you want to take that chance?

It's basically irrelevant whether you are a brain in a vat or a real being. You will continue to play the game since you are programmed to.

gurugeorge
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### Re: How do we know our reasoning is valid?

UhOH wrote:Recently I have been wracked by global scepticism, are we brains in vats, were the world and all our memories created last Thursday etc. I found that with the use of certain logical tools like Ockham's razor and abductive reasoning that I could dispel some of these sceptical doubts. But how do I know that my reasoning is true? How do I know that there isn't, say, a 100% probability that we are brains in vats? Couldn't I expand this to be more general as well, how do I know whether my deductive reasoning is valid? How do I know if any of my reasoning is true at all?
Global scepticism ceases to be compelling when you understand that its arguments are either implicitly self-contradictory or depend on the unfounded presupposition that we don't experience the world directly, but experience only our "representations" (sense data, qualia, etc.), and that we have to use those to guess at an external world.

Re. the brain in a vat, for example, there are several types of answer, depending on how the question is posed. Firstly, and generally, the brain is of course perceiving the external world (in the form of the impulses), the diabolical scientist is simply messing with the input. Brains, vats, mad scientists, computers, etc., are themselves objects in an external world, so they can't be used to cast doubt on the possibility of one, or on the possibility of demonstrating one.

And as for yourself, if someone asks you the question personally, or just generalizes it to Cartesian-Demon-like scenarios, or to "how do you know that the situation is not x logically possible scenario?", the proper response is that what is "logically possible" is so far merely imagination, and is there any reason to take that imagined scenario seriously as possible?

Also, of course, your interlocutor exists and is asking you these questions, so he's shot himself in the foot before he starts. If he suggests there's no reason why he can't be a "dream interlocutor" posing the question to a solipsistic you, then you have to ask him in what sense your experience as a whole can be "dream-like" in any meaningful way, when it bears no hallmarks of dreaming and cannot be contrasted with anything else in your experience (as dreams, normally understood, contrast with waking).

When you boil it right down, all these pseudo-problems arise from taking up the Cartesian methodologically solipsistic starting point of, "What can I know for certain?" in a certain way. If you ask that question while bracketing an external, shared reality, all you end up doing is having a nagging hankering to redefine "experience", "consciousness", etc., as things that only I can have.

Terrapin Station
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### Re: How do we know our reasoning is valid?

UhOH wrote:Recently I have been wracked by global scepticism, are we brains in vats, were the world and all our memories created last Thursday etc. I found that with the use of certain logical tools like Ockham's razor and abductive reasoning that I could dispel some of these sceptical doubts. But how do I know that my reasoning is true? How do I know that there isn't, say, a 100% probability that we are brains in vats? Couldn't I expand this to be more general as well, how do I know whether my deductive reasoning is valid? How do I know if any of my reasoning is true at all?
Validity is a specific concept in logic. And that specific concept is not what you're talking about above.

You're really just wanting to know whether any of your beliefs are true, and really this sort of crisis arises because of a desire for certainty.

In my opinion, one important step in doing philosophy is challenging that desire for certainty. Why do you feel the need for certainty, especially if it can be had for almost no beliefs? I think that going by "what has the best reasons for belief" is a better approach.

For example, regarding "brains in vats" or "the world and all our memories were created last Thursday," what would be good reasons for believing either? The mere possibility of them shouldn't be sufficient. Because it's possible that we're not brains in vats and that the world wasn't created last Thursday, too. There need to be other reasons to believe what you believe than mere possibility. Certainty (versus the lack of it) and mere possibility don't matter for belief. Good reasons, good evidence, etc. is what matters.

HexHammer
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### Re: How do we know our reasoning is valid?

UhOH wrote:Recently I have been wracked by global scepticism, are we brains in vats, were the world and all our memories created last Thursday etc. I found that with the use of certain logical tools like Ockham's razor and abductive reasoning that I could dispel some of these sceptical doubts. But how do I know that my reasoning is true? How do I know that there isn't, say, a 100% probability that we are brains in vats? Couldn't I expand this to be more general as well, how do I know whether my deductive reasoning is valid? How do I know if any of my reasoning is true at all?
Brain in a watt are for unusual stupid people, the complexity of the universe/reality exceeds that of what a brain can manufacture of false images and impressions.

To see reason from babble and lies, requires knowledge and intellect ..but most of all rationality which only so few have, why you see like 95% on various philosophy fora just doing cozy chat, babble and rave all day long, not doing philosophy which is "love of wisdom".

Arising_uk
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### Re: How do we know our reasoning is valid?

Hobbes' Choice wrote:... 1-2=1 is 100% valid. ...
?

Arising_uk
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### Re: How do we know our reasoning is valid?

HexHammer wrote:... Brain in a watt are for unusual stupid people, the complexity of the universe/reality exceeds that of what a brain can manufacture of false images and impressions. ...
If this is true how do you know it?

HexHammer
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### Re: How do we know our reasoning is valid?

Arising_uk wrote:
HexHammer wrote:... Brain in a watt are for unusual stupid people, the complexity of the universe/reality exceeds that of what a brain can manufacture of false images and impressions. ...
If this is true how do you know it?
I can't know 100%, but I just find it logically impossible.

Greta
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### Re: How do we know our reasoning is valid?

Thinking about this, I'm not sure why people come to feel the slightest doubt about the what we usually accept as reality. I've never been given any reason to doubt the veracity of reality; the cases and effects tend to make sense. Transcendent states may make normal consciousness states seem pale by comparison but everyday consciousness seems to suffice, at least for most.

I'd be interested to know what makes people doubt their reality.

Dalek Prime
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### Re: How do we know our reasoning is valid?

HexHammer wrote:Brain in a watt are for unusual stupid people