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 Exceptions to Logical Fallacies ?
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marvin
Skeptic Friend

77 Posts

Posted - 08/24/2001 :  11:07:34  Show Profile Send marvin a Private Message
quote:
“Appeal to ignorance -- the claim that whatever has not been proved false must be true, and vice versa (e.g.,There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist -- and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we're still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence.” ---Carl Sagan


"absence of evidence is not evidence of absence."


Are these logical fallacies:

All scientific theories must be falsifiable.

When testing a drug for safety, ‘absence of side effects' is evidence of the absence of side effects.

A defendant is presumed innocent until proven guilty.

~ If there really were a Bigfoot type creatures feeding, and reproducing in the Pacific Northwest, then we would have undeniable evidence of it by now.

~ We don't have undeniable evidence of Bigfoot, after more than fifty years.

~ Therefore there is no such animal.

Bigfoot does not exist, there is no empirical evidence.
=====================================================

I am searching for a ‘simplistic' way of excluding the logical fallacy ‘argument ad ignorantiam' {aka ‘apeal to ignorance'} Most ‘logical fallacy' websites do not bother to list the exceptions to the fallacy. I have only found two, that list exceptions, Gary N. Curtis and Daniel Reeders.

I am specifically looking for something similar to an “Encyclopedia of Logic” that would answer the question straightforward with no ambiguity.

Please allow me to quote my detractor:

quote:
“Marvin, there are never any exceptions to a fallacy. Let me put this another way: There is no time, place, situation, or purpose in which it is permissible to use a logical fallacy!” ---Tim


Valiant Dancer
Forum Goalie

USA
4826 Posts

Posted - 08/24/2001 :  11:46:29   [Permalink]  Show Profile  Visit Valiant Dancer's Homepage Send Valiant Dancer a Private Message
quote:

quote:
“Appeal to ignorance -- the claim that whatever has not been proved false must be true, and vice versa (e.g.,There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist -- and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we're still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence.” ---Carl Sagan


"absence of evidence is not evidence of absence."


Are these logical fallacies:

All scientific theories must be falsifiable.



This is not. It is part of the definition of the scientific method.

quote:

When testing a drug for safety, ‘absence of side effects' is evidence of the absence of side effects.



Absence of side effects in this case is proven by testing. The falsifiable part of the claim is if side effects occur in the test subjects that happen that is different or more severe than in the test subjects given a placebo. In the guide to medications put out by the AMA, there are no drugs that do not have some kind of side effect. The rating of the side effect and percentage occurance is listed in the book. The effects can be mild (dry mouth) to severe (Heart palpatations, terratogen).

quote:

A defendant is presumed innocent until proven guilty.



This is an assumption granted defendants in a criminal trial. Whether or not it is enforced is up to the individual jurors.

quote:

~ If there really were a Bigfoot type creatures feeding, and reproducing in the Pacific Northwest, then we would have undeniable evidence of it by now.

~ We don't have undeniable evidence of Bigfoot, after more than fifty years.

~ Therefore there is no such animal.

Bigfoot does not exist, there is no empirical evidence.



It can be logically inferred that a 7+foot creature existing in such numbers as to have a sustanable population would leave some form of evidence in an area as developed as reported. The evidence presented thus far has been highly suspect.

quote:

=====================================================

I am searching for a ‘simplistic' way of excluding the logical fallacy ‘argument ad ignorantiam' {aka ‘apeal to ignorance'} Most ‘logical fallacy' websites do not bother to list the exceptions to the fallacy. I have only found two, that list exceptions, Gary N. Curtis and Daniel Reeders.

I am specifically looking for something similar to an “Encyclopedia of Logic” that would answer
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marvin
Skeptic Friend

77 Posts

Posted - 08/24/2001 :  15:05:29   [Permalink]  Show Profile Send marvin a Private Message
quote:
Another type of reasoning is called "auto-epistemic" ("self-knowing") because it involves reasoning from premises about what one knows and what one would know if something were true. The form of such reasoning is:

If p were true, then I would know that p.
I don't know that p.
Therefore, p is false.

Similarly, when extensive investigation has been undertaken, it is often reasonable to infer that something is false based upon a lack of positive evidence for it. For instance, if a drug has been subjected to lengthy testing for harmful effects and none has been discovered, it is then reasonable to conclude that it is safe. Another example is:

~If there really were a large and unusual type of animal in Loch Ness, then we would have undeniable evidence of it by now.
~We don't have undeniable evidence of a large, unfamiliar animal in Loch Ness.
~Therefore, there is no such animal.

As with reasoning using the closed world assumption, auto-epistemic reasoning does not commit the fallacy of argument from ignorance. --- Gary N. Curtis


Valiant Dancer,

Thanks for your response.

Do I need to argue that ‘auto-epistemic' reasoning is an exception to the logical fallacy argumentum ad ignorantiam?

Or perhaps some other name, perhaps I'm stuck on the word 'exception', if you could point me in the right direction. I'm still looking for a ‘simplistic' explanation.

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Greg
Skeptic Friend

USA
281 Posts

Posted - 08/25/2001 :  05:17:02   [Permalink]  Show Profile  Send Greg an AOL message Send Greg a Private Message
Marvin,

Just for a simple illustration, here is an auto-epistemic argument of the form above.

1. If my wife was having an affair then I would know it.
2. I do not know that my wife is having an affair
3. Therfore, she's not.

I'm sure glad that logic would give me peace of mind here. It all depends on ones ability to know such a thing. It's a useless argument form.

As for the drug testing scenario, safety is considered based on a standard set by a regulating body (FDA in the US). The standards are essentially based on a cost-benefit (to society rather than the corporation) analysis. Every effect in every situation and every interaction could not be thoroughly tested. There would never be any new drugs on the market and that would be a high cost to society. Once the drug has met the standard as 'safe', then the reguators balance the level of safety of the drug with the level of effectiveness. Then a drug can be marketed. It can however be taken off of the market at any time by the regulators based on new data (and this does happen). The process of decision making is not as arbitrary as one might think.

Greg.

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marvin
Skeptic Friend

77 Posts

Posted - 08/25/2001 :  08:26:05   [Permalink]  Show Profile Send marvin a Private Message
quote:
“Marvin, there are never any exceptions to a fallacy. Let me put this another way: There is no time, place, situation, or purpose in which it is permissible to use a logical fallacy!” ---Tim

Is this statement 100% true?

Or is it just accurate?

Are their “exceptions” to the logical fallacy argumentum ad ignorantiam?

Is inductive reasoning a useless argument form, compared to deductive logic??
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marvin
Skeptic Friend

77 Posts

Posted - 08/25/2001 :  10:01:30   [Permalink]  Show Profile Send marvin a Private Message
‘absence of evidence is not evidence of absence'


{View 1} Since you cannot disprove that there are flying saucers, you should accept as reliable the reports of those claiming to have seen such objects.

{View 2} Flying saucers do not exist, there is no empirical evidence.

Do both of these ‘theories' commit a logical fallacy: argumentum ad ignorantiam?

"Argumentum ad ignorantium -- X is true because it has not been proven false."

Edited by - marvin on 08/25/2001 11:11:02
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Trish
SFN Addict

USA
2102 Posts

Posted - 08/25/2001 :  16:11:49   [Permalink]  Show Profile Send Trish a Private Message
Marvin,

The case of the first statements requires no supportive data and relies on allegorical evidence, for which substantive data exists showing the allegorical claims (read sightings) are subjective in nature and not always reliable.

In the case of the second, approximately 95% of UFO sightings go from being unidentified to being identified. That leaves approximately 5% of sightings remaining as UFOs. The problem here is that UFO does not equate with alien intelligence. Consider the physics involved in getting from our nearest celestial neighbor to earth. Approximately 3.9 light years separate the two objects. This would mean that figuring how to travel at near light speed they could arrive hear in approximately 4 years, however, according to relativity the time passage at Alpha Centauri would be much greater than that. What is the point of loading a ship that you expect to return with probes of humans centuries after it's launch. Except on galatic time scales that's generally too much time to wait for a return on the investment. Plus, many abduction stories include probing of sexuality and impregnation. If they're trying to save their society they had better be long lived, because the original pilots would not return for nearly 1000 years. Plus, the cost effectiveness in resourses to get a vessel traveling at light speed is (pardon the pun) astronomical.

Sorry, there are too many empirical, reproducible forms of evidence against the possibility of alien visitation. Plus, find out where the aliens are supposed to be from. I always love the *advanced* aliens that come from young hot stars.

He's YOUR god, they're YOUR rules, YOU burn in hell!
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PhDreamer
SFN Regular

USA
925 Posts

Posted - 08/25/2001 :  21:55:18   [Permalink]  Show Profile  Visit PhDreamer's Homepage Send PhDreamer a Private Message
quote:

‘absence of evidence is not evidence of absence'


{View 1} Since you cannot disprove that there are flying saucers, you should accept as reliable the reports of those claiming to have seen such objects.



This is argumentum ad ignorantiam for reasons I state below.

quote:

{View 2} Flying saucers do not exist, there is no empirical evidence.



If it is literally true that there are zero data points that support a 'flying saucer hypothesis,' then saying 'view 2' above would be the same as saying nothing. Even if the premise of 'view 2' is not strictly true, they are still not equivalent, in that 'view 1' has an a priori assumption that there exists no set of data that can verify its converse. That is the set of all possible locations and conditions in which a flying saucer might exist is essentially infinite. 'View 2' is an apparent conclusion of reason. It is probably fair to assume that a person making such a statement is doing so with respect to the locations and conditions that have been observed. It does not follow that because "there is no empirical evidence" within the observed locations and conditions that "there is no empirical evidence" within unobserved locations and conditions. In other words, 'view 2' is readily falsifiable, and the speaker surely knows such.

Do both of these ‘theories' commit a logical fallacy: argumentum ad ignorantiam?

My conclusion is no, they both do not.


This signature does not exist.
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marvin
Skeptic Friend

77 Posts

Posted - 08/27/2001 :  12:10:15   [Permalink]  Show Profile Send marvin a Private Message
Assuming this is an argument, we next differentiate between a deductive argument and inductive argument. The use of the word “empirical” leads to a pragmatic conclusion that this is an inductive argument. There are two different kinds of inductive arguments: Inductive Generalizations and Hypothetical Reasoning (a.k.a. Interpretive Arguments).

{View 2} Flying saucers do not exist, there is no empirical evidence.

This is an example of Hypothetical Reasoning. Its conclusion is "Flying saucers do not exist". It's a Descriptive Explanation. The argument has 1 premise; "There is no empirical evidence." is attempting to establish explanatory clarity by confirming the conclusion.

When analyzing Hypothetical Reasoning we look for - though we will not always find - premises that 1- attempt to confirm the conclusion, 2- attempt to disconfirm (i.e., rule out) an alternative conclusion, and/or 3- attempt to establish plausibility.

The premise is attempting to disconfirm an alternative conclusion: ‘Flying saucers exist, I have pictures, eyewitnesses, landing impressions, debris... of one.' By claiming that there is ‘no' empirical evidence available {in over fifty years} to support the alternate hypothesis.

Please critique my argument analysis, any input will be appreciated.
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PhDreamer
SFN Regular

USA
925 Posts

Posted - 08/27/2001 :  20:24:31   [Permalink]  Show Profile  Visit PhDreamer's Homepage Send PhDreamer a Private Message
quote:

Assuming this is an argument, we next differentiate between a deductive argument and inductive argument. The use of the word “empirical” leads to a pragmatic conclusion that this is an inductive argument. There are two different kinds of inductive arguments: Inductive Generalizations and Hypothetical Reasoning (a.k.a. Interpretive Arguments).

{View 2} Flying saucers do not exist, there is no empirical evidence.

This is an example of Hypothetical Reasoning. Its conclusion is "Flying saucers do not exist". It's a Descriptive Explanation. The argument has 1 premise; "There is no empirical evidence." is attempting to establish explanatory clarity by confirming the conclusion.



Well, an implied 2nd premise could be something like, "In order to conclude that flying saucers exist, we must have empirical evidence of flying saucers."

quote:

When analyzing Hypothetical Reasoning we look for - though we will not always find - premises that 1- attempt to confirm the conclusion, 2- attempt to disconfirm (i.e., rule out) an alternative conclusion, and/or 3- attempt to establish plausibility.

The premise is attempting to disconfirm an alternative conclusion: ‘Flying saucers exist, I have pictures, eyewitnesses, landing impressions, debris... of one.' By claiming that there is ‘no' empirical evidence available {in over fifty years} to support the alternate hypothesis.

Please critique my argument analysis, any input will be appreciated.



This seems to be headed down the road of statistical testing, so... strictly, if the null hypothesis is, "Flying saucers do not exist," then the only possible options are rejecting the null or accepting the null. This is a bit misleading, because the 'work' is actually done with respect to the alternate hypothesis. The null does not have to be proven true, only that the alternate is not proven true.


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marvin
Skeptic Friend

77 Posts

Posted - 08/28/2001 :  09:22:05   [Permalink]  Show Profile Send marvin a Private Message
quote:
{View 2} Flying saucers do not exist, there is no empirical evidence.

HASTY GENERALIZATION (SECUNDUM QUID)
Description: An argument in which a proposition is used as a premise without attention given to some obvious condition that would affect the proposition's application. This fallacy is also known as the "hasty generalization." It is a fallacy that takes evidence from several, possibly unrepresentative, cases to a general rule; generalizing from few to many. Note the relation to statistics: Much of statistics concerns whether or not a sample is representative of a larger population. The larger the sample size, the better the representativeness. Note also that the opposite of a hasty generalization is a sweeping generalization. ---Logical Fallacies

Here is an example of argument, which is invalid as a deductive argument but acceptable as an inductive argument:

Inductive Generalization: “Flying saucers do not exist, there is no empirical evidence.”

Unlike deductive fallacies, which are easy to point to, inductive fallacies tend to be judgement calls. Different people have different opinions about the line between correct and incorrect induction. Generally speaking, the amount of support needed to justify an inductive link is inversely related to two other factors: the plausibility of the generalization and the risk factor involved in rejecting a generalization. {null hypothesis}

Implausible inductive leaps require more evidence than plausible ones do. It requires more evidence to support the notion that a strange light in the sky is a “Flying Saucer” than the notion than it is a low-flying plane. The evidentiary requirements are greater for the first assumption simply because induction requires us to combine what we observe with what we already know, and most of us know more about low-flying planes than extra-terrestrial invaders. {a priori}

When is an Inductive Generalization valid? That is, when does an Inductive Generalization's premise(s) provide enough justification to believe that its conclusion probably is true? {empirically adequate} An Inductive Generalization is valid when its premises provide enough information to conclude 1- the sample's result sufficiently supports the argument's conclusion, 2- the sample's characteristics sufficiently support the argument's conclusion, AND 3-the sample's size sufficiently supports the argument's conclusion.
quote:
From 1947 to 1969 the U.S. Air Force investigated UFOs as a possible threat to national security. A total of 12,618 reports were received, of which 701 reports, or 5.6 percent, were listed as unexplained. The air force concluded: "no UFO reported, investigated, and evaluated by the Air Force has ever given any indication of threat to our national security."

The objects most often mistaken for UFOs are bright planets and stars, aircraft, birds, balloons, kites, aerial flares, peculiar clouds, meteors, and satellites. The remaining sightings most likely can be attributed to other mistaken sightings or to inaccurate reporting, hoaxes, or delusions, although to disprove all claims made about UFOs is impossible.

On June 24, 1947 Kenneth Arnold sighting brought "flying saucers" to national attention; "What kept bothering me as I watched them flip and flash in the sun right along their path was the fact that I couldn't make out any tail on them..." Understandably, Arnold assumed that the objects were metal craft reflecting the sunlight.
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Valiant Dancer
Forum Goalie

USA
4826 Posts

Posted - 08/28/2001 :  10:37:31   [Permalink]  Show Profile  Visit Valiant Dancer's Homepage Send Valiant Dancer a Private Message
quote:

quote:
Another type of reasoning is called "auto-epistemic" ("self-knowing") because it involves reasoning from premises about what one knows and what one would know if something were true. The form of such reasoning is:

If p were true, then I would know that p.
I don't know that p.
Therefore, p is false.

Similarly, when extensive investigation has been undertaken, it is often reasonable to infer that something is false based upon a lack of positive evidence for it. For instance, if a drug has been subjected to lengthy testing for harmful effects and none has been discovered, it is then reasonable to conclude that it is safe. Another example is:

~If there really were a large and unusual type of animal in Loch Ness, then we would have undeniable evidence of it by now.
~We don't have undeniable evidence of a large, unfamiliar animal in Loch Ness.
~Therefore, there is no such animal.

As with reasoning using the closed world assumption, auto-epistemic reasoning does not commit the fallacy of argument from ignorance. --- Gary N. Curtis


Valiant Dancer,

Thanks for your response.

Do I need to argue that ‘auto-epistemic' reasoning is an exception to the logical fallacy argumentum ad ignorantiam?

Or perhaps some other name, perhaps I'm stuck on the word 'exception', if you could point me in the right direction. I'm still looking for a ‘simplistic' explanation.





In this particular case, the appeal is not to ignorance but rather based on extensive testing on the subject. The appeal to ignorance implies very little or no testing has occurred. It relies on "gut feeling" or other forms of intuitive reasoning with no evidence. Therefore, appeal to ignorance fallacies are specific forms of flawed premise arguements. Auto-epistemic arguements have extensively tested premises.



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marvin
Skeptic Friend

77 Posts

Posted - 08/29/2001 :  11:41:08   [Permalink]  Show Profile Send marvin a Private Message
quote:
AFFIRMATION OF THE CONSEQUENT

Description: An argument from the truth of a hypothetical statement, and the truth of the consequent to the truth of the antecedent. In the syllogism below, P is the antecedent and Q is the consequent:

P implies Q
Q is true <-- Affirming the consequent
Therefore: P is true

1) Flying saucers do not exist. [because] There is no empirical evidence.
2) There is no empirical evidence.
3) Therefore: Flying saucers do not exist.

The fallacy of ‘Affirming the Consequent' is at the heart of the scientific method.

Inference to the best explanation or the hypothetico-deductive method.

This method of argument is used greatly in science. It begins with a group of phenomena, which are to be explained. In seeking to explain these phenomena a series of hypotheses are invented from which the phenomena can be deduced.

1) If H, then P.____1) If it has rained, the streets will be wet.
2) P._____________2) The streets are wet.
3) Therefore: H.____3) Therefore it has rained.

From the considerations above it follows that inference to the best explanation or the hypothetico-deductive method can reach conclusions, which are at best probable {ie a street sweeper could cause the streets to be wet}

Evaluating Inferences to Best Explanation

What do we mean by "best explanation"? I.e. under what conditions can we be confident in the truth of the second premise and thus be confident that the explanation is probably true?

Firstly, how do we evaluate them for strength?

1. They should actually explain the event in question (not stand in need of explanation themselves).
2. They should be powerful (i.e. widely applicable).
3. The simpler the better.
4. They should be conservative with respect to prior beliefs, about the natural order of things.
5. They should be testable, with some way of acquiring evidence that would tend to confirm or disconfirm the hypothesis.

Deduction (or to give it its proper name, deductive logic) is a way of making authoritative statements (proofs) about what is not known by a thorough analysis of what is known. The ability to make deductive statements is a very powerful tool since it is the basis for drawing logical conclusions about specific events from general events.

A theory, in this interpretation, consists of confirmed hypotheses, since any large-scale piece of social research it is highly unlikely that a researcher would be testing a single hypothesis. Once this stage has been reached it should be possible to make predictions about behavior based on the theory that has been developed.

{View 2} Flying saucers do not exist, there is no empirical evidence.

Is explanatory, powerful, simple, and conservative to any prior beliefs. It is a strong deductive theory that is readily falsifiable {ie produce a piece of a flying saucer, the bigger --- the better} It is an inference to the best explanation of the phenomenon of reports of “Flying Saucers”. {nomological-deductive versus historical-narrative explanations}

This argument analysis may be the most accurate? But not the most ‘simplistic'
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