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What do you think?

  1. Nov 27, 2004 #1
    We have a life form that can think.
    If the life form can think it must have the power of reason.
    The power of reason would permit a 3rd fact being obtained from 2 other facts.
    The life form would be aware of its ability of deduction.
    The life form would be aware of itself.
    The life form would be an intelligent life form.
    Therefore a life form that can think is an intelligent life form.
    Could anybody find a flaw in this logic please.
     
  2. jcsd
  3. Nov 27, 2004 #2
    Well for one thing, this "intelligence" could be a machine. In which case it would neither be aware of its own existance, nor of its ability to use immediate inference and syllogistic reasoning.
     
  4. Nov 29, 2004 #3

    honestrosewater

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    Ian,
    First things first. Some of these terms are already well-defined; Life is one them. But others do not come with precise definitions. I've listed them below. Please define them as precisely as you can.

    think
    "power of reason"
    aware
    deduction or "ability of deduction"
    itself (aware of itself as a "life form" and/or its "power of reason"?)
    intelligent or "intelligent life form"

    Have fun :biggrin:
    ____
    dekoi,
    Why not?
     
  5. Nov 29, 2004 #4

    Tom Mattson

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    This is really a question in epistemology, so I'm scooting it out of the Logic forum. It's actually (sorta) related to a topic that I find very interesting called the epistemic closure principle. I'll kick in a couple of pennies when I get home from work.

    Uh oh, boss is coming... :redface:
     
  6. Nov 29, 2004 #5

    Les Sleeth

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    Tom, in anticipation of an interesting post, I hope you don't mind if I add a small challenge for you to include in your answer.

    From the empirical point of view can inference ever be considered knowledge? If we toss out the extreme brain-in-a-vat skeptic and just allow reasonable skepticism (i.e., skepticism that admits we exist, that experience provides a healthy consciousness with a close approximation of reality and, consequently, that we can trust that those aspects of reality we do experience actually exist), then can't the certainty of any inference be undermined?

    I am not suggesting inference has no practical utility, like when a mother finds a heavily snoring son, smelling of beer, 30 beer cans on the floor . . . she needs to rely on inference to decide if he needs help, or a scolding. But we know she could be wrong too. He might have decided to start collecting beer cans to suppliment his income, got a bunch of beer on himself collecting, and wore himself out looking for them.

    It seems to me that closure is only possible by direct observation, and this idea of logical closure can never produce true knowledge. Once experiential tracking is stopped, then we've left the realm of knowing and entered the realm of (at best) reasonable assumptions.
     
    Last edited: Nov 30, 2004
  7. Nov 30, 2004 #6
    It does not necessarily follow that the ability to think implies the ability to reason. This would depend on your definition of think.

    I think the last two sentences are inverted. I think to be aware of its ability to reason it must first be self aware. Does the ability to reason imply awareness, either self awareness or awareness that it is reasoning? I don't know. It does not IMO logically follow without further proof and precise definitions

    This again would depend on your unstated definition of intelligent. Is a thinking, reasoning, aware life form intelligent? I would say yes; but, that is just my opinion not logic.

    Given the above, I think that this conclusion would be contained in the definitions and unproven assumptions.

    Tom, I eagerly await your expert comments and lecture on epistemic closure principle.
     
  8. Nov 30, 2004 #7
    I did a quick Goggle search on epistemic closure and this is what I came up with. From the AMERICAN PHILOSOPHICAL QUARTERLY, Vol. 22 No. 1 Jan 1985. It is a quote taken from an article by Radu J. Bogdan.

    My first response was the ubiquitous; "HUH?" :confused: : After reading it several times I think that I got it and yes it applies beautifully to the starting post of this thread.

    Tom, I hope that I am not stepping all over your proposed post. I really am anxious to read it.
     
  9. Dec 1, 2004 #8

    Tom Mattson

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    OK, thanks. But I'm certainly no expert, and I'll probably have more questions than answers. It will have to wait until the weekend though. I've got a lot of work to do until then.

    You'll note that this is an inductive inference. I'll be talking about deduction.

    But why, if a proposition is deduced from 1 or more propositions that are known by direct experience? Deductive validity forces a conclusion to be true if it is derived from true premises.

    I'll post the whole thing over the weekend. (By the way, I didn't say that I accept the closure principle, only that I think it is interesting).
     
  10. Dec 2, 2004 #9
    Definition of Terms-May I suggest.
    Think-Being able to imagine reality.
    Power of reason- Being able to juggle imagined reality.
    Aware- Believing 'I think therefore I am'
    Deduction- Being able to juggle imagined reality and come to a correct solution in reality.
    Itself-Being aware,as defined above.
    Intelligent life form- Itself deducting-as defined above.
    So, is a life form that can think an intelligent life form? inference and syllogism notwithstanding?
     
  11. Dec 2, 2004 #10

    loseyourname

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    If you want an evaluation of the logic here, you're going to have to translate this into a truth-functional argument that can be represented symbolically or at least into some evaluable series of syllogisms. I could probably do it myself, but I'm not convinced it would be easy or even that it would accurate reflect your intentions.
     
  12. Dec 3, 2004 #11

    Les Sleeth

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    Okay. I tend to turn everything into induction probably because that's what I like most. :tongue2:


    You as a mathematician are probably a lot more comfortable than I am with abstractions. I am one of those guys who skims any explanation looking for a real life example. When you find time to get back to this, I hope you will include an example.

    My only skepticism now is that I've not found an unobserved prediction from true premises that cannot be undermined. It is one thing to say the logic is correct, and another to say the conclusion reached actually has a corresponding aspect in reality.

    If you recall my post, I said I can see practical value of assuming (for practical purposes of calculating) that something which has been a certain way in the past will continue to be so in the future. But even if past consistancy gives us great confidence in our calculations, we cannot truly know if the prediction is correct from logic alone. This is just me arguing my little radical experientialist theory that nothing can be known unless it is experienced.
     
  13. Dec 3, 2004 #12

    honestrosewater

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    Ian,
    Obviously I agree with loseyourname, but you shouldn't be discouraged. Your argument may be conceptually correct, despite any fault in its formal construction. I can't wait for this discussion to really get going, and I hope you stick around for it :biggrin: As Les and Tom have pointed out, "deduction" does have a precise definition in logic (as contrasted with "induction"). Maybe you should look up those terms and decide which one you want, if any.
    Les,
    Does your skepticism concern our ability to a) prove the truth of a premise or b) prove the validity of a deductive argument? In other words, do you doubt the certainty of our knowledge about reality or about logic? Or do you class logic with reality?
     
  14. Dec 3, 2004 #13

    Les Sleeth

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    My skepticism has to do with what Tom brought up, the epistemic closure principle, and specifically what constitutes closure. The simple version of the epistemic closure idea is, if we know something to be true, and it implies something else is true, can we assume the "something else" is known (closure); that is, what is the so-called "epistemic value" of what is implied?.

    As I said to Tom, I am a concrete example kind of thinker, so I started looking around the net for some examples to help me explain my objections. After I found an article that expresses my own opinion about the epistemic value of inference I decided to recommend that. You can find the article at:

    http://64.233.161.104/search?q=cach...emic+closure+principle+example&hl=en&ie=UTF-8

    In a nutshell, my own view is that deductive inference is only perfectly valid for mathematical functions. The example in the article was that if 2+3=5, then that implies 3+2=5, which is indisputable. However, once one begins reasoning about actual, existing situations in the real world (i.e., outside the internal operations of math/logic), my experientialist streak says one must observe/experience what's been inferred before it can be considered "known." Now, that doesn't mean what's implied has no empistemic value.

    Say a man is brought to a doctor who's just been bitten by an insane gang of 30 sea snakes. It is logical for the doctor to assume the man is at risk of death and, given what we know about the toxicity of sea snake venom, that the man will likely not survive. Yet what she actually knows (her observation of 30 sea snake bites) and what's implied by what she knows (that the man's life is in danger) do not have equal epistemic value. What if, after examining the man, she finds out that there was no venom in the bites because the insane gang of sea snakes had just finished attacking a whale and used up all their venom? Or what if it turns out the man has a weird metabolism and sea snake venom is no problem for him?

    Of course, both those exceptions are unlikely. Therefore for practical purposes it is justified for the doctor to treat what's only implied as actually "known," and so prepare to doctor the man in such a way that is assists him in fighting for his life.
     
    Last edited: Dec 3, 2004
  15. Dec 3, 2004 #14

    honestrosewater

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    Les,
    I prefer to stay in the formal logic world as much as possible, but I'll try it the other way. Variety is the spice of life, right? :approve:
    The example given ("3+2=5" entails "2+3=5") has no epistemic value unless evaluated in terms of other logical statements, in this case axioms, and notably the commutative property of addition. In other words, it
    Have I misunderstood something? Perhaps the point is that we can theoretically know everything in the formal world, but not in the physical world. And I'm not yet sure that's true.

    In your snake bite example, the doctor makes inductive inferences, notably that the presence of bite wounds implies the presence of venom. I doubt she could tell they were sea snake bite wounds either- the size of the fangs would be the only evidence I can think of which could be precise enough (quantifiable, measurable to a given degree of precision), and the variation of fang size within sea snakes and all fanged snakes should make a unique match impossible. Even if the person was bitten while in waters sea snakes are known to inhabit, and so on...
    However, if the victim observed everything possible for him to observe about the snakes that bit him, the situation gets interesting.
    P: every observable fact about the snakes that bit him
    Q: every observable fact about all snakes
    Assuming the victim knows p, and the doctor knows q. Can they figure out what kind of snake bit him?
    Some terms need to be defined and some assumptions made explicit, but that's part of the fun.
     
  16. Dec 3, 2004 #15

    loseyourname

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    The doctor can test the venom to determine what species of snake bit him.
     
  17. Dec 3, 2004 #16

    Les Sleeth

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    You are close. My point is that we can know that our logic is correct, but we cannot know if the conclusion of correct premises corresponds to an actual circumstance in reality. I emphasized "corresponds" to let you know my preference for determining the truth of statements is the correspondence theory of truth. That is, a statement is true when it corresponds with the way reality actually is.

    Consider the example of 3+2=5 entails 2+3=5. In the world of math/logic, it is a perfect inference. Will physical reality correspond every time to that statement? Notice the only difference is the order of 2 and 3. Let's say in reality there is a combination of two materials, 2 pints of one, and three pints of the other, that is altered by which is added to the other; the 2+3 order produces 5 pints, but 3+2 order causes one material to absorb more of other and consequently reduces the overall volume from 5 to 4.9.

    For me, logic is nothing without an actual reality to relate it to. Another variety of thinker believes reason alone can produce truths. I have never been able to accept that.


    Let's take away all the ambiguity except what the issue is we are trying to decide. Let's say the doctor was diving with her husband, and it was he who got bit. The doctor is also a herpetologist, has perfect vision, can count to 30, and recognized the snakes. Since she herself witnessed the event, the doctor is certain 30 sea snakes bit the man. Let's add one more fact. No sea snake has ever been observed biting a human without injecting venom.

    To restate your statement in terms of my question of closure:

    P: every observable fact about the snakes that bit him
    Q: every PAST observable fact about all snakes ("past" is added because all we know for certain is how things have been)

    Assuming the doctor knows P and Q, does she know her husband's life is in danger? Or is it the case that rather than "know," the doctor is "reasonably certain" her husband's life is in danger?
     
    Last edited: Dec 3, 2004
  18. Dec 3, 2004 #17

    loseyourname

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    You're referring to the difference between a valid and a sound argument. A valid argument is one in which if the premises are all true, then the conclusion must also be true. A sound argument is a valid argument with all true premises. Take the following arguments:

    If a human fetus is a person, then it has rights.
    A human fetus is a person.
    Therefore, a human fetus has rights.

    This is a valid argument (Modus Ponens, actually), but it is not sound because we do not know whether the component premises are true and so we cannot draw any conclusion from it that we know is in accordance with reality.

    All men are mortal.
    Les is a man.
    Therefore, Les is mortal.

    This is a valid argument (in this case, it requires a translation into quantificational language, then we can prove it using Universal Instantiation and Modus Ponens) and it is a sound argument, because the two premises used to draw the conclusion are both true. Men are mortal and Les is a man. Because of this, even though we have not observed your death, we can be certain that you will die.
     
  19. Dec 3, 2004 #18

    Les Sleeth

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    I don't believe one can exactly equate the correspondence theory of truth to a sound argument because correspondence is mostly an epistomological issue (though some might say it is semantic too) while soundness is a logic issue. Correspondence describes the relationship between a concept and reality. It is epistomological because it assumes there is a reliable avenue for getting an image of reality into one's head (i.e., experience) to use for conceptualization. Soundness in an argument, as you say, describes the use of correct premises (which, if one is an empiricist, are established by correspondence) with correct logic.
     
  20. Dec 3, 2004 #19

    honestrosewater

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    Oh, that is so cheating. :approve: Okay, assuming the victim's knoweldge is the doctor's only source of knowledge about the source of the poison.
     
  21. Dec 3, 2004 #20

    loseyourname

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    All right, so let me get this into my own words (always helps me). What you're discussing is the determination of truth value for individual propositions, not the derivation of true conclusions from true premises.
     
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