Circular nature of logic.

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Consider the following syllogism:



premises:



$1.$ $A$ is a man.



$2.$ Every man has a heart.



Conclusion:



$3.$ $A$ has a heart.



Logic says that $1$ and $2$ allows us to come to the conclusion that $3$ is true. But, first of all how did we know $A$ is a man? If $A$ doesn't have a heart, we don't call him a man in the first place right?



I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic. May be, in the development of logic, mathematicians may have encountered that problem and questioned such bases that logic is built.



My Question:



Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).




logic




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  • 7




    You told your Readers (myself included) that A is a man. I only know this because you told me. It makes little sense to tell me that, then ask "how we knew A is a man."
    – hardmath
    Jul 27 at 4:42






  • 1




    You are welcome to post suitable Questions on Math.SE, but anyone will be free to post answers. Be sure to review the Tour of Math.SE to get a better idea of what excellent Questions will look like.
    – hardmath
    Jul 27 at 4:52






  • 1




    @JMoravitz It may help you more to ask the question in your native language That's risky advice around MSE, judging by the quick close votes to that edit.
    – dxiv
    Jul 27 at 5:22







  • 2




    @dxiv You might not have seen some of the earlier comments made by the OP, but I am not convinced that the OP can understand more than half of the words of any given sentence being said here, much less the nuances in language necessary to adequately convey mathematical concepts in logic rigorously. There were a good half-dozen comments from the OP, each of which with only half of the words spelled correctly (poplem instead of problem, queschen instead of question) where the OP claimed that noone else who speaks their native language studies math in the whole world.
    – JMoravitz
    Jul 27 at 5:44







  • 2




    the implication is that somehow through an act of the universe, A was created and he is a man and he has a heart and hair and toenails and somehow the universe decreed that being a man means you have a heart. And somehow the universe slapped you awake and said "Hey, acquire! Every man has a heart. So says the universe" and then the universe tosses A at you and say "Hey! acquire! The is A-- he is a man" and now you are left shaken awake with only a brain, memory, and logic. You conclude, "well, he's a man and all men have hearts so he must have a heart...."
    – fleablood
    Jul 27 at 7:33















up vote
-4
down vote

favorite












Consider the following syllogism:



premises:



$1.$ $A$ is a man.



$2.$ Every man has a heart.



Conclusion:



$3.$ $A$ has a heart.



Logic says that $1$ and $2$ allows us to come to the conclusion that $3$ is true. But, first of all how did we know $A$ is a man? If $A$ doesn't have a heart, we don't call him a man in the first place right?



I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic. May be, in the development of logic, mathematicians may have encountered that problem and questioned such bases that logic is built.



My Question:



Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).




logic




share|cite|improve this question

















  • 7




    You told your Readers (myself included) that A is a man. I only know this because you told me. It makes little sense to tell me that, then ask "how we knew A is a man."
    – hardmath
    Jul 27 at 4:42






  • 1




    You are welcome to post suitable Questions on Math.SE, but anyone will be free to post answers. Be sure to review the Tour of Math.SE to get a better idea of what excellent Questions will look like.
    – hardmath
    Jul 27 at 4:52






  • 1




    @JMoravitz It may help you more to ask the question in your native language That's risky advice around MSE, judging by the quick close votes to that edit.
    – dxiv
    Jul 27 at 5:22







  • 2




    @dxiv You might not have seen some of the earlier comments made by the OP, but I am not convinced that the OP can understand more than half of the words of any given sentence being said here, much less the nuances in language necessary to adequately convey mathematical concepts in logic rigorously. There were a good half-dozen comments from the OP, each of which with only half of the words spelled correctly (poplem instead of problem, queschen instead of question) where the OP claimed that noone else who speaks their native language studies math in the whole world.
    – JMoravitz
    Jul 27 at 5:44







  • 2




    the implication is that somehow through an act of the universe, A was created and he is a man and he has a heart and hair and toenails and somehow the universe decreed that being a man means you have a heart. And somehow the universe slapped you awake and said "Hey, acquire! Every man has a heart. So says the universe" and then the universe tosses A at you and say "Hey! acquire! The is A-- he is a man" and now you are left shaken awake with only a brain, memory, and logic. You conclude, "well, he's a man and all men have hearts so he must have a heart...."
    – fleablood
    Jul 27 at 7:33













up vote
-4
down vote

favorite









up vote
-4
down vote

favorite











Consider the following syllogism:



premises:



$1.$ $A$ is a man.



$2.$ Every man has a heart.



Conclusion:



$3.$ $A$ has a heart.



Logic says that $1$ and $2$ allows us to come to the conclusion that $3$ is true. But, first of all how did we know $A$ is a man? If $A$ doesn't have a heart, we don't call him a man in the first place right?



I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic. May be, in the development of logic, mathematicians may have encountered that problem and questioned such bases that logic is built.



My Question:



Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).




logic




share|cite|improve this question













Consider the following syllogism:



premises:



$1.$ $A$ is a man.



$2.$ Every man has a heart.



Conclusion:



$3.$ $A$ has a heart.



Logic says that $1$ and $2$ allows us to come to the conclusion that $3$ is true. But, first of all how did we know $A$ is a man? If $A$ doesn't have a heart, we don't call him a man in the first place right?



I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic. May be, in the development of logic, mathematicians may have encountered that problem and questioned such bases that logic is built.



My Question:



Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).





logic





share|cite|improve this question












share|cite|improve this question




share|cite|improve this question








edited Jul 30 at 17:31
























asked Jul 27 at 4:37









aquire

147




147







  • 7




    You told your Readers (myself included) that A is a man. I only know this because you told me. It makes little sense to tell me that, then ask "how we knew A is a man."
    – hardmath
    Jul 27 at 4:42






  • 1




    You are welcome to post suitable Questions on Math.SE, but anyone will be free to post answers. Be sure to review the Tour of Math.SE to get a better idea of what excellent Questions will look like.
    – hardmath
    Jul 27 at 4:52






  • 1




    @JMoravitz It may help you more to ask the question in your native language That's risky advice around MSE, judging by the quick close votes to that edit.
    – dxiv
    Jul 27 at 5:22







  • 2




    @dxiv You might not have seen some of the earlier comments made by the OP, but I am not convinced that the OP can understand more than half of the words of any given sentence being said here, much less the nuances in language necessary to adequately convey mathematical concepts in logic rigorously. There were a good half-dozen comments from the OP, each of which with only half of the words spelled correctly (poplem instead of problem, queschen instead of question) where the OP claimed that noone else who speaks their native language studies math in the whole world.
    – JMoravitz
    Jul 27 at 5:44







  • 2




    the implication is that somehow through an act of the universe, A was created and he is a man and he has a heart and hair and toenails and somehow the universe decreed that being a man means you have a heart. And somehow the universe slapped you awake and said "Hey, acquire! Every man has a heart. So says the universe" and then the universe tosses A at you and say "Hey! acquire! The is A-- he is a man" and now you are left shaken awake with only a brain, memory, and logic. You conclude, "well, he's a man and all men have hearts so he must have a heart...."
    – fleablood
    Jul 27 at 7:33













  • 7




    You told your Readers (myself included) that A is a man. I only know this because you told me. It makes little sense to tell me that, then ask "how we knew A is a man."
    – hardmath
    Jul 27 at 4:42






  • 1




    You are welcome to post suitable Questions on Math.SE, but anyone will be free to post answers. Be sure to review the Tour of Math.SE to get a better idea of what excellent Questions will look like.
    – hardmath
    Jul 27 at 4:52






  • 1




    @JMoravitz It may help you more to ask the question in your native language That's risky advice around MSE, judging by the quick close votes to that edit.
    – dxiv
    Jul 27 at 5:22







  • 2




    @dxiv You might not have seen some of the earlier comments made by the OP, but I am not convinced that the OP can understand more than half of the words of any given sentence being said here, much less the nuances in language necessary to adequately convey mathematical concepts in logic rigorously. There were a good half-dozen comments from the OP, each of which with only half of the words spelled correctly (poplem instead of problem, queschen instead of question) where the OP claimed that noone else who speaks their native language studies math in the whole world.
    – JMoravitz
    Jul 27 at 5:44







  • 2




    the implication is that somehow through an act of the universe, A was created and he is a man and he has a heart and hair and toenails and somehow the universe decreed that being a man means you have a heart. And somehow the universe slapped you awake and said "Hey, acquire! Every man has a heart. So says the universe" and then the universe tosses A at you and say "Hey! acquire! The is A-- he is a man" and now you are left shaken awake with only a brain, memory, and logic. You conclude, "well, he's a man and all men have hearts so he must have a heart...."
    – fleablood
    Jul 27 at 7:33








7




7




You told your Readers (myself included) that A is a man. I only know this because you told me. It makes little sense to tell me that, then ask "how we knew A is a man."
– hardmath
Jul 27 at 4:42




You told your Readers (myself included) that A is a man. I only know this because you told me. It makes little sense to tell me that, then ask "how we knew A is a man."
– hardmath
Jul 27 at 4:42




1




1




You are welcome to post suitable Questions on Math.SE, but anyone will be free to post answers. Be sure to review the Tour of Math.SE to get a better idea of what excellent Questions will look like.
– hardmath
Jul 27 at 4:52




You are welcome to post suitable Questions on Math.SE, but anyone will be free to post answers. Be sure to review the Tour of Math.SE to get a better idea of what excellent Questions will look like.
– hardmath
Jul 27 at 4:52




1




1




@JMoravitz It may help you more to ask the question in your native language That's risky advice around MSE, judging by the quick close votes to that edit.
– dxiv
Jul 27 at 5:22





@JMoravitz It may help you more to ask the question in your native language That's risky advice around MSE, judging by the quick close votes to that edit.
– dxiv
Jul 27 at 5:22





2




2




@dxiv You might not have seen some of the earlier comments made by the OP, but I am not convinced that the OP can understand more than half of the words of any given sentence being said here, much less the nuances in language necessary to adequately convey mathematical concepts in logic rigorously. There were a good half-dozen comments from the OP, each of which with only half of the words spelled correctly (poplem instead of problem, queschen instead of question) where the OP claimed that noone else who speaks their native language studies math in the whole world.
– JMoravitz
Jul 27 at 5:44





@dxiv You might not have seen some of the earlier comments made by the OP, but I am not convinced that the OP can understand more than half of the words of any given sentence being said here, much less the nuances in language necessary to adequately convey mathematical concepts in logic rigorously. There were a good half-dozen comments from the OP, each of which with only half of the words spelled correctly (poplem instead of problem, queschen instead of question) where the OP claimed that noone else who speaks their native language studies math in the whole world.
– JMoravitz
Jul 27 at 5:44





2




2




the implication is that somehow through an act of the universe, A was created and he is a man and he has a heart and hair and toenails and somehow the universe decreed that being a man means you have a heart. And somehow the universe slapped you awake and said "Hey, acquire! Every man has a heart. So says the universe" and then the universe tosses A at you and say "Hey! acquire! The is A-- he is a man" and now you are left shaken awake with only a brain, memory, and logic. You conclude, "well, he's a man and all men have hearts so he must have a heart...."
– fleablood
Jul 27 at 7:33





the implication is that somehow through an act of the universe, A was created and he is a man and he has a heart and hair and toenails and somehow the universe decreed that being a man means you have a heart. And somehow the universe slapped you awake and said "Hey, acquire! Every man has a heart. So says the universe" and then the universe tosses A at you and say "Hey! acquire! The is A-- he is a man" and now you are left shaken awake with only a brain, memory, and logic. You conclude, "well, he's a man and all men have hearts so he must have a heart...."
– fleablood
Jul 27 at 7:33











2 Answers
2






active

oldest

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2
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But, first of all how did we know $A$ is a man?




For example because someone told us that $A$ is a man.




If $A$ doesn't have a heart, we don't call him a man in the first place right?




Well, assuming the second claim, “Every man has a heart”, is true, then from $A$ not having a heart we can conclude that $A$ is not a man. And yes, that second claim might well come directly from a definition.




I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic.




Quite the opposite, it's actually the strength of logic. It means that we don't need to know anything about men or hearts to know that anyone who claims at the same time that $A$ is a man, that all men have hearts, and that $A$ has no heart, must be wrong.




Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).




It is not a circular reasoning because there's no circle in it. It would only be circular reasoning if before we had used $A$ having a heart in order to determine that $A$ is a man. But we didn't; that fact was just given.



Note that also in real life we usually don't check whether someone has a heart when we determine whether he is a man. Rather we look at their outside, and draw our conclusions from that. The heart is not seen from the outside.






share|cite|improve this answer























  • Note that also in real life ... not seen from the outside. It's a bit confusing now. So are you telling that $A$ might not have a heart at all? So current logic may claim wrong conclusions. Is that what you meant? Is it not a discrepancy of current logic? Either the reasoning is circular or current logic can claim unreasonable conclusions. That's what I am getting right now. :-(
    – aquire
    Jul 27 at 20:20











  • @aquire: No, all I'm saying is that you usually don't check whether someone has a heart before you decide he's a man. At least I assume you're not running around with a stethoscope to check whether people around you have hearts, are you?
    – celtschk
    Jul 28 at 0:06










  • ...you usually don't check whether someone has a heart before you decide he's a man. If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart? Consider an ideal humanoid $colorredA$. Just by looking outside appearance one comes to the conclusion that $colorredA$ is a man. Then our premise is wrong. So our conclusion is wrong. That means this is just circular reasoning. i.e. if $colorredA$ don't have a heat then $colorredA$ don't have a heart. Am I wrong? I'm really really confused. ;-(
    – aquire
    Jul 28 at 3:47










  • “If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart?” — That doesn't follow. For example, say I have irrefutable proof that only men have beards. Then as soon as I determine that someone has a beard, I can conclude that he is a man. And if I in addition know without doubt that all men have hearts, I can conclude that he has a heart. Not that I never explicitly checked that he has a heart; I only checked he has a beard.
    – celtschk
    Jul 28 at 6:35











  • But of course, if the assumptions are wrong, then the conclusions don't follow. But that's not a failure of logic, that's making wrong assumptions. There's still nothing circular, as there's still no circle. Note however that, contrary to your claim, from the falsity of the assumptions it does not follow that the conclusion is wrong. For example, for a woman we may incorrectly think she's a man. And then from that incorrect assumption conclude that she has a heart. Does this imply that she has no heart? Obviously not.
    – celtschk
    Jul 28 at 6:41


















up vote
1
down vote













In logic there are certain given facts, which are facts that are assumed true, and then there are claims, which we are trying to prove. In saying that $1)$ and $2)$ lead to $3)$, you are using $1)$ and $2)$ as the given statements, so it is assumed that $A$ is a man, and therefore has a heart.






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    2 Answers
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    active

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    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

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    active

    oldest

    votes








    up vote
    2
    down vote














    But, first of all how did we know $A$ is a man?




    For example because someone told us that $A$ is a man.




    If $A$ doesn't have a heart, we don't call him a man in the first place right?




    Well, assuming the second claim, “Every man has a heart”, is true, then from $A$ not having a heart we can conclude that $A$ is not a man. And yes, that second claim might well come directly from a definition.




    I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic.




    Quite the opposite, it's actually the strength of logic. It means that we don't need to know anything about men or hearts to know that anyone who claims at the same time that $A$ is a man, that all men have hearts, and that $A$ has no heart, must be wrong.




    Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).




    It is not a circular reasoning because there's no circle in it. It would only be circular reasoning if before we had used $A$ having a heart in order to determine that $A$ is a man. But we didn't; that fact was just given.



    Note that also in real life we usually don't check whether someone has a heart when we determine whether he is a man. Rather we look at their outside, and draw our conclusions from that. The heart is not seen from the outside.






    share|cite|improve this answer























    • Note that also in real life ... not seen from the outside. It's a bit confusing now. So are you telling that $A$ might not have a heart at all? So current logic may claim wrong conclusions. Is that what you meant? Is it not a discrepancy of current logic? Either the reasoning is circular or current logic can claim unreasonable conclusions. That's what I am getting right now. :-(
      – aquire
      Jul 27 at 20:20











    • @aquire: No, all I'm saying is that you usually don't check whether someone has a heart before you decide he's a man. At least I assume you're not running around with a stethoscope to check whether people around you have hearts, are you?
      – celtschk
      Jul 28 at 0:06










    • ...you usually don't check whether someone has a heart before you decide he's a man. If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart? Consider an ideal humanoid $colorredA$. Just by looking outside appearance one comes to the conclusion that $colorredA$ is a man. Then our premise is wrong. So our conclusion is wrong. That means this is just circular reasoning. i.e. if $colorredA$ don't have a heat then $colorredA$ don't have a heart. Am I wrong? I'm really really confused. ;-(
      – aquire
      Jul 28 at 3:47










    • “If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart?” — That doesn't follow. For example, say I have irrefutable proof that only men have beards. Then as soon as I determine that someone has a beard, I can conclude that he is a man. And if I in addition know without doubt that all men have hearts, I can conclude that he has a heart. Not that I never explicitly checked that he has a heart; I only checked he has a beard.
      – celtschk
      Jul 28 at 6:35











    • But of course, if the assumptions are wrong, then the conclusions don't follow. But that's not a failure of logic, that's making wrong assumptions. There's still nothing circular, as there's still no circle. Note however that, contrary to your claim, from the falsity of the assumptions it does not follow that the conclusion is wrong. For example, for a woman we may incorrectly think she's a man. And then from that incorrect assumption conclude that she has a heart. Does this imply that she has no heart? Obviously not.
      – celtschk
      Jul 28 at 6:41















    up vote
    2
    down vote














    But, first of all how did we know $A$ is a man?




    For example because someone told us that $A$ is a man.




    If $A$ doesn't have a heart, we don't call him a man in the first place right?




    Well, assuming the second claim, “Every man has a heart”, is true, then from $A$ not having a heart we can conclude that $A$ is not a man. And yes, that second claim might well come directly from a definition.




    I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic.




    Quite the opposite, it's actually the strength of logic. It means that we don't need to know anything about men or hearts to know that anyone who claims at the same time that $A$ is a man, that all men have hearts, and that $A$ has no heart, must be wrong.




    Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).




    It is not a circular reasoning because there's no circle in it. It would only be circular reasoning if before we had used $A$ having a heart in order to determine that $A$ is a man. But we didn't; that fact was just given.



    Note that also in real life we usually don't check whether someone has a heart when we determine whether he is a man. Rather we look at their outside, and draw our conclusions from that. The heart is not seen from the outside.






    share|cite|improve this answer























    • Note that also in real life ... not seen from the outside. It's a bit confusing now. So are you telling that $A$ might not have a heart at all? So current logic may claim wrong conclusions. Is that what you meant? Is it not a discrepancy of current logic? Either the reasoning is circular or current logic can claim unreasonable conclusions. That's what I am getting right now. :-(
      – aquire
      Jul 27 at 20:20











    • @aquire: No, all I'm saying is that you usually don't check whether someone has a heart before you decide he's a man. At least I assume you're not running around with a stethoscope to check whether people around you have hearts, are you?
      – celtschk
      Jul 28 at 0:06










    • ...you usually don't check whether someone has a heart before you decide he's a man. If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart? Consider an ideal humanoid $colorredA$. Just by looking outside appearance one comes to the conclusion that $colorredA$ is a man. Then our premise is wrong. So our conclusion is wrong. That means this is just circular reasoning. i.e. if $colorredA$ don't have a heat then $colorredA$ don't have a heart. Am I wrong? I'm really really confused. ;-(
      – aquire
      Jul 28 at 3:47










    • “If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart?” — That doesn't follow. For example, say I have irrefutable proof that only men have beards. Then as soon as I determine that someone has a beard, I can conclude that he is a man. And if I in addition know without doubt that all men have hearts, I can conclude that he has a heart. Not that I never explicitly checked that he has a heart; I only checked he has a beard.
      – celtschk
      Jul 28 at 6:35











    • But of course, if the assumptions are wrong, then the conclusions don't follow. But that's not a failure of logic, that's making wrong assumptions. There's still nothing circular, as there's still no circle. Note however that, contrary to your claim, from the falsity of the assumptions it does not follow that the conclusion is wrong. For example, for a woman we may incorrectly think she's a man. And then from that incorrect assumption conclude that she has a heart. Does this imply that she has no heart? Obviously not.
      – celtschk
      Jul 28 at 6:41













    up vote
    2
    down vote










    up vote
    2
    down vote










    But, first of all how did we know $A$ is a man?




    For example because someone told us that $A$ is a man.




    If $A$ doesn't have a heart, we don't call him a man in the first place right?




    Well, assuming the second claim, “Every man has a heart”, is true, then from $A$ not having a heart we can conclude that $A$ is not a man. And yes, that second claim might well come directly from a definition.




    I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic.




    Quite the opposite, it's actually the strength of logic. It means that we don't need to know anything about men or hearts to know that anyone who claims at the same time that $A$ is a man, that all men have hearts, and that $A$ has no heart, must be wrong.




    Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).




    It is not a circular reasoning because there's no circle in it. It would only be circular reasoning if before we had used $A$ having a heart in order to determine that $A$ is a man. But we didn't; that fact was just given.



    Note that also in real life we usually don't check whether someone has a heart when we determine whether he is a man. Rather we look at their outside, and draw our conclusions from that. The heart is not seen from the outside.






    share|cite|improve this answer
















    But, first of all how did we know $A$ is a man?




    For example because someone told us that $A$ is a man.




    If $A$ doesn't have a heart, we don't call him a man in the first place right?




    Well, assuming the second claim, “Every man has a heart”, is true, then from $A$ not having a heart we can conclude that $A$ is not a man. And yes, that second claim might well come directly from a definition.




    I know that in propositional logic we don't question the premises. We just take them as they are without questioning the basis of such sentences. I think it is an inherent problem of logic.




    Quite the opposite, it's actually the strength of logic. It means that we don't need to know anything about men or hearts to know that anyone who claims at the same time that $A$ is a man, that all men have hearts, and that $A$ has no heart, must be wrong.




    Although this is considered as a valid reasoning in current logic, I claim that this is yet another circular reasoning in disguise. Disprove that (using current logic or any other paradigm for that matter).




    It is not a circular reasoning because there's no circle in it. It would only be circular reasoning if before we had used $A$ having a heart in order to determine that $A$ is a man. But we didn't; that fact was just given.



    Note that also in real life we usually don't check whether someone has a heart when we determine whether he is a man. Rather we look at their outside, and draw our conclusions from that. The heart is not seen from the outside.







    share|cite|improve this answer















    share|cite|improve this answer



    share|cite|improve this answer








    edited Jul 27 at 20:17









    amWhy

    189k25219431




    189k25219431











    answered Jul 27 at 13:38









    celtschk

    28.1k65495




    28.1k65495











    • Note that also in real life ... not seen from the outside. It's a bit confusing now. So are you telling that $A$ might not have a heart at all? So current logic may claim wrong conclusions. Is that what you meant? Is it not a discrepancy of current logic? Either the reasoning is circular or current logic can claim unreasonable conclusions. That's what I am getting right now. :-(
      – aquire
      Jul 27 at 20:20











    • @aquire: No, all I'm saying is that you usually don't check whether someone has a heart before you decide he's a man. At least I assume you're not running around with a stethoscope to check whether people around you have hearts, are you?
      – celtschk
      Jul 28 at 0:06










    • ...you usually don't check whether someone has a heart before you decide he's a man. If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart? Consider an ideal humanoid $colorredA$. Just by looking outside appearance one comes to the conclusion that $colorredA$ is a man. Then our premise is wrong. So our conclusion is wrong. That means this is just circular reasoning. i.e. if $colorredA$ don't have a heat then $colorredA$ don't have a heart. Am I wrong? I'm really really confused. ;-(
      – aquire
      Jul 28 at 3:47










    • “If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart?” — That doesn't follow. For example, say I have irrefutable proof that only men have beards. Then as soon as I determine that someone has a beard, I can conclude that he is a man. And if I in addition know without doubt that all men have hearts, I can conclude that he has a heart. Not that I never explicitly checked that he has a heart; I only checked he has a beard.
      – celtschk
      Jul 28 at 6:35











    • But of course, if the assumptions are wrong, then the conclusions don't follow. But that's not a failure of logic, that's making wrong assumptions. There's still nothing circular, as there's still no circle. Note however that, contrary to your claim, from the falsity of the assumptions it does not follow that the conclusion is wrong. For example, for a woman we may incorrectly think she's a man. And then from that incorrect assumption conclude that she has a heart. Does this imply that she has no heart? Obviously not.
      – celtschk
      Jul 28 at 6:41

















    • Note that also in real life ... not seen from the outside. It's a bit confusing now. So are you telling that $A$ might not have a heart at all? So current logic may claim wrong conclusions. Is that what you meant? Is it not a discrepancy of current logic? Either the reasoning is circular or current logic can claim unreasonable conclusions. That's what I am getting right now. :-(
      – aquire
      Jul 27 at 20:20











    • @aquire: No, all I'm saying is that you usually don't check whether someone has a heart before you decide he's a man. At least I assume you're not running around with a stethoscope to check whether people around you have hearts, are you?
      – celtschk
      Jul 28 at 0:06










    • ...you usually don't check whether someone has a heart before you decide he's a man. If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart? Consider an ideal humanoid $colorredA$. Just by looking outside appearance one comes to the conclusion that $colorredA$ is a man. Then our premise is wrong. So our conclusion is wrong. That means this is just circular reasoning. i.e. if $colorredA$ don't have a heat then $colorredA$ don't have a heart. Am I wrong? I'm really really confused. ;-(
      – aquire
      Jul 28 at 3:47










    • “If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart?” — That doesn't follow. For example, say I have irrefutable proof that only men have beards. Then as soon as I determine that someone has a beard, I can conclude that he is a man. And if I in addition know without doubt that all men have hearts, I can conclude that he has a heart. Not that I never explicitly checked that he has a heart; I only checked he has a beard.
      – celtschk
      Jul 28 at 6:35











    • But of course, if the assumptions are wrong, then the conclusions don't follow. But that's not a failure of logic, that's making wrong assumptions. There's still nothing circular, as there's still no circle. Note however that, contrary to your claim, from the falsity of the assumptions it does not follow that the conclusion is wrong. For example, for a woman we may incorrectly think she's a man. And then from that incorrect assumption conclude that she has a heart. Does this imply that she has no heart? Obviously not.
      – celtschk
      Jul 28 at 6:41
















    Note that also in real life ... not seen from the outside. It's a bit confusing now. So are you telling that $A$ might not have a heart at all? So current logic may claim wrong conclusions. Is that what you meant? Is it not a discrepancy of current logic? Either the reasoning is circular or current logic can claim unreasonable conclusions. That's what I am getting right now. :-(
    – aquire
    Jul 27 at 20:20





    Note that also in real life ... not seen from the outside. It's a bit confusing now. So are you telling that $A$ might not have a heart at all? So current logic may claim wrong conclusions. Is that what you meant? Is it not a discrepancy of current logic? Either the reasoning is circular or current logic can claim unreasonable conclusions. That's what I am getting right now. :-(
    – aquire
    Jul 27 at 20:20













    @aquire: No, all I'm saying is that you usually don't check whether someone has a heart before you decide he's a man. At least I assume you're not running around with a stethoscope to check whether people around you have hearts, are you?
    – celtschk
    Jul 28 at 0:06




    @aquire: No, all I'm saying is that you usually don't check whether someone has a heart before you decide he's a man. At least I assume you're not running around with a stethoscope to check whether people around you have hearts, are you?
    – celtschk
    Jul 28 at 0:06












    ...you usually don't check whether someone has a heart before you decide he's a man. If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart? Consider an ideal humanoid $colorredA$. Just by looking outside appearance one comes to the conclusion that $colorredA$ is a man. Then our premise is wrong. So our conclusion is wrong. That means this is just circular reasoning. i.e. if $colorredA$ don't have a heat then $colorredA$ don't have a heart. Am I wrong? I'm really really confused. ;-(
    – aquire
    Jul 28 at 3:47




    ...you usually don't check whether someone has a heart before you decide he's a man. If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart? Consider an ideal humanoid $colorredA$. Just by looking outside appearance one comes to the conclusion that $colorredA$ is a man. Then our premise is wrong. So our conclusion is wrong. That means this is just circular reasoning. i.e. if $colorredA$ don't have a heat then $colorredA$ don't have a heart. Am I wrong? I'm really really confused. ;-(
    – aquire
    Jul 28 at 3:47












    “If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart?” — That doesn't follow. For example, say I have irrefutable proof that only men have beards. Then as soon as I determine that someone has a beard, I can conclude that he is a man. And if I in addition know without doubt that all men have hearts, I can conclude that he has a heart. Not that I never explicitly checked that he has a heart; I only checked he has a beard.
    – celtschk
    Jul 28 at 6:35





    “If the determination process doesn't involve checking the heart, isn't there a probability that the person not having a heart?” — That doesn't follow. For example, say I have irrefutable proof that only men have beards. Then as soon as I determine that someone has a beard, I can conclude that he is a man. And if I in addition know without doubt that all men have hearts, I can conclude that he has a heart. Not that I never explicitly checked that he has a heart; I only checked he has a beard.
    – celtschk
    Jul 28 at 6:35













    But of course, if the assumptions are wrong, then the conclusions don't follow. But that's not a failure of logic, that's making wrong assumptions. There's still nothing circular, as there's still no circle. Note however that, contrary to your claim, from the falsity of the assumptions it does not follow that the conclusion is wrong. For example, for a woman we may incorrectly think she's a man. And then from that incorrect assumption conclude that she has a heart. Does this imply that she has no heart? Obviously not.
    – celtschk
    Jul 28 at 6:41





    But of course, if the assumptions are wrong, then the conclusions don't follow. But that's not a failure of logic, that's making wrong assumptions. There's still nothing circular, as there's still no circle. Note however that, contrary to your claim, from the falsity of the assumptions it does not follow that the conclusion is wrong. For example, for a woman we may incorrectly think she's a man. And then from that incorrect assumption conclude that she has a heart. Does this imply that she has no heart? Obviously not.
    – celtschk
    Jul 28 at 6:41











    up vote
    1
    down vote













    In logic there are certain given facts, which are facts that are assumed true, and then there are claims, which we are trying to prove. In saying that $1)$ and $2)$ lead to $3)$, you are using $1)$ and $2)$ as the given statements, so it is assumed that $A$ is a man, and therefore has a heart.






    share|cite|improve this answer

























      up vote
      1
      down vote













      In logic there are certain given facts, which are facts that are assumed true, and then there are claims, which we are trying to prove. In saying that $1)$ and $2)$ lead to $3)$, you are using $1)$ and $2)$ as the given statements, so it is assumed that $A$ is a man, and therefore has a heart.






      share|cite|improve this answer























        up vote
        1
        down vote










        up vote
        1
        down vote









        In logic there are certain given facts, which are facts that are assumed true, and then there are claims, which we are trying to prove. In saying that $1)$ and $2)$ lead to $3)$, you are using $1)$ and $2)$ as the given statements, so it is assumed that $A$ is a man, and therefore has a heart.






        share|cite|improve this answer













        In logic there are certain given facts, which are facts that are assumed true, and then there are claims, which we are trying to prove. In saying that $1)$ and $2)$ lead to $3)$, you are using $1)$ and $2)$ as the given statements, so it is assumed that $A$ is a man, and therefore has a heart.







        share|cite|improve this answer













        share|cite|improve this answer



        share|cite|improve this answer











        answered Jul 27 at 4:45









        高田航

        1,116318




        1,116318






















             

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