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Friday, November 14, 2008 - 1:22pmSanction this postReply
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I got this message via my personal page which has a summary of logical fallacies:

A friend and I are quarreling over something which might (or might not) be a question of logic. One thinks that it is illogical to say that we've proven that there is no afterlife. Another says that to believe that we've proven that there is no afterlife is the only logical way to think. So I have two questions for you (if you'd be so kind).

First, is this a question of logic?

Second, whether it's a question of logic or not, do you think one side or the other represents better thinking?


Strictly speaking, proving a negative is impossible.

For example, suppose I say, "There are unicorns on Mars. Don't believe me? Prove me wrong."

Strictly speaking, this qualifies as an arbitrary assertion rather than a false one. Because the burden of proof falls on the shoulders of the person making the assertion, it would fall to me to demonstrate the truth of my statement with concrete evidence. You would have no obligation to investigate the issue yourself but would instead rightly dismiss my arbitrary assertion without further discussion, consideration, or argument.

So the issue of an afterlife amounts to an issue of how logically to handle arbitrary assertions. Anyone who claims such an existence would need to produce evidence to support that claim, beginning with a concrete definition of exactly what an "afterlife" is. However, the only way to state that an afterlife is false is to show that it contradicts reality in some way and therefore could not be true.

The Law of Identity, A is A, simply says that contradictions do not exist in reality. Thinking clearly about this issue leads to three basic axioms of existence that anyone arguing about anything must accept in order even to argue:

* Existence, i.e. that an objective world exists "out there"
* Identity, i.e. the law of non-contradiction
* Consciousness, i.e. one's awareness of reality and its non-contradictory nature

I recommend Atlas Shrugged or other books by Ayn Rand to gain some insight into this mode of thinking logically.

EDIT: Based on the subsequent posts in this thread, I should qualify my classification of the "unicorns on Mars" proposition as "arbitrary" based on no further context. In other words, if one fails to name the basic axioms as final arbiters of truth and falsehood, then yes, my proposition is arbitrary. Otherwise, as other posters have noted, it is provably false.

Now do the same exercise with the proposition, "An afterlife exists."

(Edited by Luke Setzer on 11/15, 8:11am)


Post 1

Friday, November 14, 2008 - 1:35pmSanction this postReply
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If someone were to ask me, "Are there unicorns on Mars?" would it be illogical to answer, "I don't know"?

Post 2

Friday, November 14, 2008 - 4:21pmSanction this postReply
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I'm not sure how Luke would respond, but I'm going to stick my neck out and say yes, that would be an illogical answer.

Unicorns do not exist. Period.


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Post 3

Friday, November 14, 2008 - 4:37pmSanction this postReply
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Interesting issue. I'd say that one can indeed prove that there is no afterlife.

An afterlife implies that the soul survives the body. But it is logically impossible for the soul to survive the body, because the soul depends on the body for its very existence. Therefore, it follows that there is no afterlife. This does not amount to "proving a negative" -- to refuting a claim which there is no evidence for or against -- since there is already enough evidence to demonstrate that the claim is false.

As for the claim that there are unicorns on Mars, we already have enough evidence to show that it would impossible for a horse-like creature to survive there. So, one can say with confidence that that claim is false as well. Of course, this doesn't adequately address the point of the example.

A better example would be the claim that there are unicorns on another (earth-like) planet somewhere else in the universe. As to the truth of that claim, I think it would be proper to plead ignorance. Of course, since there is no evidence in favor of it, the claim itself is unwarranted, and cannot properly be asserted as true, although it may be true, since one can't rule it out.

- Bill
(Edited by William Dwyer on 11/14, 7:07pm)

(Edited by William Dwyer on 11/14, 10:46pm)


Post 4

Friday, November 14, 2008 - 5:05pmSanction this postReply
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The use of the concept "unicorn" is messing with my head.  For example, replace unicorn with "bacteria," and suddenly the answer isn't so illogical to me.

Trust me, Bill. There are no unicorns anywhere in the universe. I'm quite certain.


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Post 5

Friday, November 14, 2008 - 6:59pmSanction this postReply
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Teresa,

Well, a unicorn is simply a horse with a single horn. Why is it impossible for such a creature to evolve in a hospitable environment? There are many bizarre deep sea creatures, much stranger looking than a unicorn, that one would never have expected to see, but there they are. For example, http://www.oddee.com/item_79915.aspx

If it's possible for these fantastic looking sea creatures to evolve on earth, why is it impossible for a strange creature, like a unicorn, to have evolved on another planet?

Suppose that human beings had yet to discover a horned mammal, like a deer or an antelope, but that someone conceived of one and drew a picture of it. Since it had never actually been observed, would you say that you were certain it doesn't exist?

Are you certain that there are no rational animals elsewhere in the universe that do not resemble human beings?

- Bill



Post 6

Friday, November 14, 2008 - 7:14pmSanction this postReply
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Isn't there some sort of rule about continuing to argue after someone has said "Trust me"? Like it's unspeakably rude or something?

You're in for it now Bill...

Post 7

Friday, November 14, 2008 - 7:28pmSanction this postReply
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Mike,

I think that rule only applies in that way with wives and girlfriends. Whereas for used car salesman, or politicians, that same phrase means you need to resist more firmly.

So, Bill might only be in trouble with Teresa if she is fond of him and he keeps arguing after she says, "Trust me"

:-)

Post 8

Friday, November 14, 2008 - 8:22pmSanction this postReply
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What about unicows?



Post 9

Friday, November 14, 2008 - 9:44pmSanction this postReply
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I would agree with Teresa - biologically, there is no validity for the development of a unicorn on land... yes, there is a one-horned rhino, but there is a validity for that, which would not apply to something horselike, namely the 'digger' attribute that a low-slung four footer could foster...   dual horns - perhaps - as per bovines or deer, where their development followed a pattern which advanced their survival...

Post 10

Friday, November 14, 2008 - 9:49pmSanction this postReply
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Bill,

urQ But it is logically impossible for the soul...

I suspect your definition of soul does not conform to the predominant religious view of "soul". If not, I'm not sure if one can understand what you mean. If so, then the logic is faulty because religions generally do not consider the soul dependent upon the body. Thus I would agree that this would still be an issue of trying to prove the negative.

jt
(Edited by Jay Abbott on 11/14, 9:52pm)


Post 11

Friday, November 14, 2008 - 9:50pmSanction this postReply
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Yes, unicows! You see, you never know!

The next thing you'll be telling me, Teresa, is that there is no Pinocchio, and that I should trust you on that!

Well, of course, we know that Pinocchio lives, and so when I see your nose growing longer, I'll know not to trust you, something I could only have learned from Pinocchio himself!

- Bill

Post 12

Friday, November 14, 2008 - 11:08pmSanction this postReply
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In Post 3, I wrote: "An afterlife implies that the soul survives the body. But it is logically impossible for the soul to survive the body, because the soul depends on the body for its very existence. Therefore, it follows that there is no afterlife. This does not amount to 'proving a negative' -- to refuting a claim which there is no evidence for or against -- since there is already enough evidence to demonstrate that the claim is false."

Jay replied,
I suspect your definition of soul does not conform to the predominant religious view of "soul". If not, I'm not sure if one can understand what you mean. If so, then the logic is faulty because religions generally do not consider the soul dependent upon the body. Thus I would agree that this would still be an issue of trying to prove the negative.
On the contrary, my definition of 'soul' does conform to the predominant religious view, which recognizes the soul as one's spirit or consciousness. My disagreement with religion lies not with its concept of the soul as a spirit or consciousness, but with its belief that it is possible for a person's spirit or consciousness to survive death. In fact, it is not possible for one's consciousness to survive the death of one's body, because a consciousness cannot exist without a viable physical body. It requires a functioning brain, sense organs, nerves, blood vessels and all the other physical preconditions of a living organism. Once the body dies, the soul (i.e., consciousness) dies along with it.

- Bill

Post 13

Saturday, November 15, 2008 - 2:59amSanction this postReply
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I hope the people who asked me the original question have learned from this thread.

It illustrates the importance of the basic axioms -- existence, identity, consciousness -- in grounding logical arguments back to reality.

Without reality as the final reference, logical arguments become floating abstractions with no meaning.

I appreciate the participation of others in this thread.

Post 14

Saturday, November 15, 2008 - 4:54amSanction this postReply
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Bill,

urQ the predominant religious view, which recognizes the soul as one's spirit or consciousness.
But I don't think that is quite the religious view. I think you have inferred it because of your leanings toward logic. In any case, I don't know I'm any more qualified to say what the correct religious view is (is there a clergyman in the house?). Therefore you don't really have to listen to me.

I suspect instead we've just made Luke's point (post #13) that when the grounding arguments are not based upon reality, any logical arguments that follow become meaningless.

Thanks, Luke. for the reminder.

jt



Post 15

Friday, November 14, 2008 - 7:12pmSanction this postReply
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Yeah! What he said!

:-)
Linda
(Edited by Linda Velasquez on 11/15, 6:52am)


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Post 16

Saturday, November 15, 2008 - 6:43amSanction this postReply
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(I adore Bill)

Bill,
Isn't it true that logic would be useless if the concepts involved couldn't be universally defined?

(Mine)

"U-ni-corn" - noun


1.a mythical creature resembling a horse, with a single horn in the center of its forehead: often symbolic of chastity or purity.
2.a heraldic representation of this animal, in the form of a horse with a lion's tail and with a long, straight, and spirally twisted horn.
3.(initial capital letter) Astronomy. the constellation Monoceros.
4.an animal mentioned in the Bible, Deut. 33:17: now believed by some to be a description of a wild ox or rhinoceros.
5.a former gold coin of Scotland, first issued by James III in 1486, having an obverse bearing the figure of a unicorn.


From The Art of Reasoning (by David Kelley, PhD. Linda, this is a very useful textbook ;):

"One major function of definitions is to tell us what is and is not included in a concept, by giving us a test or rule for membership."

"A second function of a definition is to clarify the relationships among concepts."

"A third function of a definition is to provide a summary statement about the referents of our concepts."

Is a single horn sufficient for definition?  No. The differentia is massive between single horned entities. A single horn, in my opinion, is misplacing the genus of a unicorn. The genus of a unicorn lies in fiction, and I think it's a mistake to smuggle it into the realm of reality, and an even bigger mistake to claim I just don't know something.  I do know, Bill.

"A definition should include a genus and a differentia."

There's a reason scientists give different names to similar entities. They don't call all single horned entities "unicorns."  A single horn is an attribute, not a definition.  The sum is more than it's parts, in other words.

What is the genus and differentia of a unicorn?  Define it, conceptually, and then tell me I don't know.


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Post 17

Saturday, November 15, 2008 - 10:17amSanction this postReply
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I said that the predominant religious view recognizes the soul as one's spirit or consciousness. Jay replied, "But I don't think that is quite the religious view. I think you have inferred it because of your leanings toward logic." Well, what is it that is supposed to survive death and experience the afterlife, if not one's spirit or consciousness? Recognizing that no such survival is possible would refute the possibility of an afterlife. When one's physical body dies, one's capacity for experiencing reality dies along with it.

Teresa, thanks for the definitions of "unicorn." I had no idea that the term could refer to so many different things. I was alluding to Definition 1: "A mythical creature resembling a horse, with a single horn in the center of its forehead." The point I was making is only that one can't be sure that a horse-like creature resembling a unicorn -- resembling a mythical creature -- doesn't actually exist somewhere else in the universe. It is your view, I take it, that, based on the definition of a unicorn as a mythical creature, one can be sure that no such creature exists in reality, because mythical creatures, by definition, don't exist in the real world. If that is your argument, then I would certainly agree that a creature that is only mythical (and, therefore, not real) does not exist in the real world. But I wasn't saying that a mythical creature, qua mythical creature, might exist in the real world. I was saying that a creature resembling a mythical unicorn might exist in the real world (e.g., on a distant planet).

Thanks also for the citation from Kelley's book on Logic, an excellent text, which I highly recommend. Referring to Kelley's discussion of definitions, you wrote,
Is a single horn sufficient for definition? No. The differentia is massive between single horned entities. A single horn, in my opinion, is misplacing the genus of a unicorn. The genus of a unicorn lies in fiction, and I think it's a mistake to smuggle it into the realm of reality, and an even bigger mistake to claim I just don't know something. I do know, Bill.

"A definition should include a genus and a differentia."

There's a reason scientists give different names to similar entities. They don't call all single horned entities "unicorns." A single horn is an attribute, not a definition. The sum is more than it's parts, in other words.

What is the genus and differentia of a unicorn? Define it, conceptually, and then tell me I don't know.
I agree that single horn does not define a unicorn. As Robert Malcom pointed out, there exists a single-horned rhino, which is certainly not a unicorn. And I agree that, defined as a mythical creature, the genus of a unicorn lies in fiction. So, in that sense of the term, one definition of a unicorn is, as I acknowledged above, "a mythical creature resembling a horse, with a single horn in the center of its forehead." Given this definition, I take it that the genus is "a mythical creature," and the differentia, "a horse-like creature with a single horn in the center of its forehead."

But, again, my point was not that a unicorn qua mythical creature might exist in reality, but that a creature resembling a unicorn might exist in reality. Would you still say you are certain that even that is not true?

- Bill

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Saturday, November 15, 2008 - 9:56amSanction this postReply
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I edited post 15 three hours ago, but the edit hasn't shown up yet.  Will it ever?

Post 19

Saturday, November 15, 2008 - 11:38amSanction this postReply
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But, again, my point was not that a unicorn qua mythical creature might exist in reality, but that a creature resembling a unicorn might exist in reality. Would you still say you are certain that even that is not true?

Yes, because as you've already pointed out, conditions on Mars are not conducive to anything mammalian, thus, I know nothing remotely unicornish could exist there. :)


 


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