Argument from ignorance - AbsoluteAstronomy.com

Argument from ignorance, also known as argumentum ad ignorantiam or "appeal to ignorance" (where "ignorance" stands for: "lack of evidence to the contrary"), is a fallacy in informal logic

Informal fallacy

An informal fallacy is an argument whose stated premises fail to support their proposed conclusion. The deviation in an informal fallacy often stems from a flaw in the path of reasoning that links the premises to the conclusion...

. It asserts that a proposition is true because it has not yet been proven false, it is "generally accepted" (or vice versa). This represents a type of false dichotomy in that it excludes a third option, which is that there is insufficient investigation and therefore insufficient information to prove the proposition satisfactorily to be either true or false. Nor does it allow the admission that the choices may in fact not be two (true or false), but may be as many as four, (1) true, (2) false, (3) unknown between true or false, and (4) being unknowable (among the first three). In debates, appeals to ignorance are sometimes used to shift the burden of proof.

Argument from ignorance may be used as a rationalization by a person who realizes that he has no reason for holding the belief that he does.

The fallaciousness of arguments from ignorance does not mean that one can never possess good reasons for thinking that something does not exist

Evidence of absence

Evidence of absence is evidence of any kind that suggests the non-existence or non-presence of something. A simple example of evidence of absence: checking one's pocket for spare change and finding nothing but being confident that one would have found it if it were there...

, an idea captured by philosopher Bertrand Russell's teapot

Russell's teapot

In 1958 Russell elaborated on the analogy as a reason for his own atheism:- Analysis :Peter Atkins said that the point of Russell's teapot is that no one can prove a negative, and therefore Occam's razor suggests that the more simple theory should trump the more complex theory...

, a hypothetical china teapot revolving about the sun between Earth and Mars; however this would fall more duly under the arena of pragmatism

Pragmatism

Pragmatism is a philosophical tradition centered on the linking of practice and theory. It describes a process where theory is extracted from practice, and applied back to practice to form what is called intelligent practice...

, wherein a position must be demonstrated or proven in order to be upheld, and therefore the burden of proof is on the argument's proponent.

Basic argument

Arguments that appeal to ignorance rely merely on the fact that the veracity of the proposition is not disproven to arrive at a definite conclusion. These arguments fail to appreciate that the limits of one's understanding or certainty do not change what is true

Truth

Truth has a variety of meanings, such as the state of being in accord with fact or reality. It can also mean having fidelity to an original or to a standard or ideal. In a common usage, it also means constancy or sincerity in action or character...

. They do not inform upon reality. That is, whatever the reality is, it does not “wait” upon human logic or analysis to be formulated. Reality exists at all times, and it exists independently of what is in the mind of anyone. And the true thrust of science and rational analysis is to separate preconceived notion(s) of what reality is, and to be open at all times to the observation of nature as it behaves, so as truly to discover reality. This fallacy can be very convincing and is considered by some to be a special case of a false dilemma or false dichotomy in that they both fail to consider alternatives. A false dilemma may take the form:

If a proposition has not been disproven, then it cannot be considered false and must therefore be considered true.
If a proposition has not been proven, then it cannot be considered true and must therefore be considered false.

Such arguments attempt to exploit the facts that (a) true things can never be disproven and (b) false things can never be proven. In other words, appeals to ignorance claim that the converse of these facts are also true (therein lies the fallacy).

To reiterate, these arguments ignore the fact, and difficulty, that some true things may never be proven, and some false things may never be disproved with absolute certainty

Certainty

Certainty can be defined as either:# perfect knowledge that has total security from error, or# the mental state of being without doubtObjectively defined, certainty is total continuity and validity of all foundational inquiry, to the highest degree of precision. Something is certain only if no...

.
The phrase "absence of evidence is not evidence of absence
Evidence of absence
Evidence of absence is evidence of any kind that suggests the non-existence or non-presence of something. A simple example of evidence of absence: checking one's pocket for spare change and finding nothing but being confident that one would have found it if it were there...

" can be used as a shorthand rebuttal to the second form of the ignorance fallacy (i.e. P has never been absolutely proven and is therefore certainly false.). Most often it is directed at any conclusion derived from null
Null
-In computing:* Null , a special marker and keyword in SQL* Null character, the zero-valued ASCII character, also designated by NUL, often used as a terminator, separator or filler* Null device, a special computer file that discards all data written to it...

results in an experiment or from the non-detection of something. In other words, where one researcher may say their experiment suggests evidence of absence, another researcher might argue that the experiment failed to detect a phenomenon for other reasons.

Matters of confusion

Much confusion about 'arguments from ignorance' can be caused when one side of a debate forgets that we often possess evidence of absence

Evidence of absence

in practice.

The ignorance fallacy is sometimes confused (or combined) with logically valid contrapositive arguments. Contrapositive arguments rightly utilize the transposition

Transposition (logic)

In the methods of deductive reasoning in classical logic, transposition is the rule of inference that permits one to infer from the truth of "A implies B" the truth of "Not-B implies not-A", and conversely. Its symbolic expression is:...

rule of inference in classical logic to conclude something like: To the extent that C implies E then Not-E must also imply Not-C. In other words, if a cause always leads to an effect, then absence of the expected effect is evidence of absence

Evidence of absence

of the cause. For example, if the causal proposition that If it's raining outside then the streets will be wet is assumed, then it can be assumed that if the streets are not wet then it is not raining outside. The inference that it cannot be raining outside because the streets are not getting wet is exactly as true, or perhaps exactly as untrue, as the original proposition. The statements are logically equivalent

Contraposition

In traditional logic, contraposition is a form of immediate inference in which from a given proposition another is inferred having for its subject the contradictory of the original predicate, and in some cases involving a change of quality . For its symbolic expression in modern logic see the rule...

.
As Carl Sagan

Carl Sagan

Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...

explains:

For instance, absence of evidence that it rained (i.e. water is the evidence) may be considered as positive evidence that it did not rain. Again, in science, such inferences are always made to some limited (sometimes extremely high) degree of probability

Probability

Probability is ordinarily used to describe an attitude of mind towards some proposition of whose truth we arenot certain. The proposition of interest is usually of the form "Will a specific event occur?" The attitude of mind is of the form "How certain are we that the event will occur?" The...

.

Arguments from ignorance can easily find their way into debates over the Existence of God

Existence of God

Arguments for and against the existence of God have been proposed by philosophers, theologians, scientists, and others. In philosophical terms, arguments for and against the existence of God involve primarily the sub-disciplines of epistemology and ontology , but also of the theory of value, since...

. It is a fallacy to draw conclusions based precisely on ignorance, since this does not satisfactorily address issues of philosophic burden of proof

Philosophic burden of proof

The philosophic burden of proof is the obligation on a party in an epistemic dispute to provide sufficient warrant for their position.-Holder of the burden:When debating any issue, there is an implicit burden of proof on the person asserting a claim...

. In other words, agnosticism

Agnosticism

Agnosticism is the view that the truth value of certain claims—especially claims about the existence or non-existence of any deity, but also other religious and metaphysical claims—is unknown or unknowable....

is an appropriate response to lack of evidence either way.

Contraposition and Transposition

Contraposition is a logically valid rule of inference that allows the creation of a new proposition from the negation and reordering of an existing one. The method applies to any proposition of the type If A then B and says that negating all the variables and switching them back to front leads to a new proposition i.e. If Not-B then Not-A that is just as true as the original one and that the first implies the second and the second implies the first.

Transposition

Transposition (logic)

is exactly the same thing described in a different language.

Absence of evidence

Absence of evidence is the absence, or lack of, any kind of evidence that may show, indicate, suggest, or be used to infer or deduce a fact.

Evidence of absence

Evidence of absence is evidence of any kind that can be used to infer or deduce the non-existence or non-presence of something. For instance, if a doctor does not find any malignant cells in a patient this null result

Null result

In science, a null result is a result without the expected content: that is, the proposed result is absent. It is an experimental outcome which does not show an otherwise expected effect. This does not imply a result of zero or nothing, simply a result that does not support the hypothesis...

(finding nothing) is evidence of absence of cancer, even though the doctor has not actually detected anything per se. Such inductive reasoning

Inductive reasoning

Inductive reasoning, also known as induction or inductive logic, is a kind of reasoning that constructs or evaluates propositions that are abstractions of observations. It is commonly construed as a form of reasoning that makes generalizations based on individual instances...

is important to empiricism

Empiricism

Empiricism is a theory of knowledge that asserts that knowledge comes only or primarily via sensory experience. One of several views of epistemology, the study of human knowledge, along with rationalism, idealism and historicism, empiricism emphasizes the role of experience and evidence,...

and science, but has well established limitations. The challenge thus becomes to try to identify when a researcher has received a null result (found nothing) because the thing does not exist (evidence of absence), and when one simply lacks proper means of detection (absence of evidence).

Negative evidence

Negative evidence is sometimes used as an alternative to absence of evidence and is often meant to be synonymous with it. On the other hand, the term may also refer to evidence with a negative value, or null result equivalent to evidence of absence. It may even refer to positive evidence about something of an unpleasant nature.

Null result

Null result is a term often used in the field of science to indicate absence of evidence. A search for water on the ground may yield a null result (the ground is dry); therefore, it probably did not rain.

Argument from incredulity/Lack of imagination

Arguments from incredulity take the form:

P is too incredible (or: I cannot imagine how P could possibly be true); therefore P must be false.
It is obvious that P (or: I cannot imagine how P could possibly be false); therefore P must be true.

These arguments are similar to arguments from ignorance in that they too ignore and do not properly eliminate the possibility that something can be both incredible and still be true, or appear to be obvious and yet still be false.

Argument from self-knowing (auto-epistemic)

Arguments from self-knowing take the form:

If P were true then I would know it; in fact I do not know it; therefore P cannot be true.
If P were false then I would know it; in fact I do not know it; therefore P cannot be false.

In practice these arguments are often fallacious and rely on the veracity of the supporting premise. For example the argument that If I had just sat on a wild porcupine
Porcupine
Porcupines are rodents with a coat of sharp spines, or quills, that defend or camouflage them from predators. They are indigenous to the Americas, southern Asia, and Africa. Porcupines are the third largest of the rodents, behind the capybara and the beaver. Most porcupines are about long, with...

then I would know it; in fact I do not know it; therefore I did not just sit on a wild porcupine is probably not a fallacy and depends entirely on the veracity of the leading proposition that supports it. (See Contraposition

Contraposition

and Transposition

Transposition (logic)

in the Related terms section in this article.)

Distinguishing absence of evidence from evidence of absence

Absence of Evidence is a condition in which no valid conclusion can be inferred from the mere absence of detection, normally due to doubt in the detection method. Evidence of absence
Evidence of absence
Evidence of absence is evidence of any kind that suggests the non-existence or non-presence of something. A simple example of evidence of absence: checking one's pocket for spare change and finding nothing but being confident that one would have found it if it were there...

is the successful variation: a conclusion that relies on specific knowledge in conjunction with negative detection to deduce the absence of something. An example of evidence of absence is checking your pockets for spare change and finding nothing but being confident that the search would have found it if it was there.

Formal argument

By determining that a given experiment or method of detection is sensitive and reliable enough to detect the presence of X (when X is present) one can confidently exclude the possibility that X may be both undetected and present. This allows one to deduce that X cannot be present if a null result is received.

Thus there are only two possibilities, given a null result:

Nothing detected, and X is not present.
Nothing detected, but X is present (Option eliminated by careful research design).

To the extent that option 2 can be eliminated, one can deduce that if X is not detected then X is not present and therefore the null result

Null result

is evidence of absence

Evidence of absence

Absence of evidence

(These examples contain or represent missing information.)

Statements that begin with "I can't prove it but…" are often referring to some kind absence of evidence.
"There is no evidence of foul play here" is a direct reference to the absence of evidence.

Negative results

When the doctor says that the test results were negative, it is usually good news.
Under "Termites" the inspector checked the box that read "no".
The results of Michelson–Morley's experiment reported no shift at all in the interference pattern.

Evidence of absence

(These examples contain definite evidence that can be used to show, indicate, suggest, infer or deduce the non-existence or non-presence of something.)

A biopsy shows the absence of malignant cells.
The null result found by Michelson–Morley's famous experiment represents "strong evidence" that the luminiferous aether
Luminiferous aether
In the late 19th century, luminiferous aether or ether, meaning light-bearing aether, was the term used to describe a medium for the propagation of light....

was not present.
One very carefully inspects the back seat of one's car and finds no tigers.
The train schedule does not say that the train stops here at 3:00pm on a Sunday.

Arguments from ignorance

(Draws a conclusion based on lack of knowledge or evidence without accounting for all possibilities)

"I take the view that this lack (of enemy subversive activity in the west coast) is the most ominous sign in our whole situation. It convinces me more than perhaps any other factor that the sabotage we are to get, the Fifth Column activities are to get, are timed just like Pearl Harbor... I believe we are just being lulled into a false sense of security." – Then California's Attorney General Earl Warren
Earl Warren
Earl Warren was the 14th Chief Justice of the United States.He is known for the sweeping decisions of the Warren Court, which ended school segregation and transformed many areas of American law, especially regarding the rights of the accused, ending public-school-sponsored prayer, and requiring...

(before a congressional hearing in San Francisco on 21 February 1942)

In the field of science

One looks in the back seat of one's car and finds no adult-sized kangaroo
Kangaroo
A kangaroo is a marsupial from the family Macropodidae . In common use the term is used to describe the largest species from this family, especially those of the genus Macropus, Red Kangaroo, Antilopine Kangaroo, Eastern Grey Kangaroo and Western Grey Kangaroo. Kangaroos are endemic to the country...

s and then uses this negative/null adult-sized kangaroo detection results in conjunction with the previously determined fact (or just plain old proposition) that adult-sized kangaroos, if present, cannot evade such detection, to deduce a new fact that there are indeed no adult-sized kangaroos present in the back seat of said car.

Principles in law

The presumption of innocence, if present, effectively removes the possibility that the accused may be both guilty and unproven, from consideration in judgment, and as such the accused is considered as innocent unless proven guilty. (See decision table below)
1. Innocent and unproven. Judged as innocent.
2. Innocent and proven. Judged as guilty. (Jury is biased, misled, makes error; law is incorrect; false evidence fabricated etc.)
3. Guilty and unproven. Judged as innocent. (Presumption of innocence)
4. Guilty and proven. Judged as guilty. (Innocent unless/until proven guilty is a summary of this and easier to remember.)

Origin of the term

From "Fallacies: classical and contemporary readings By Hans V. Hansen, Robert C. Pinto"

"It is generally accepted that the philosopher John Locke

John Locke

John Locke FRS , widely known as the Father of Liberalism, was an English philosopher and physician regarded as one of the most influential of Enlightenment thinkers. Considered one of the first of the British empiricists, following the tradition of Francis Bacon, he is equally important to social...

introduced the term in his Essay Concerning Human Understanding:"

"Another way that Men ordinarily use to drive others, and force them to submit their Judgments. And receive the Opinion in debate, is to require the Adversary to admit what they alledge as a Proof, or assign a better. And this I call Argumentum ad Ignorantum" – John Locke

Sources

Fallacies: classical and contemporary readings By Hans V. Hansen, Robert C. Pinto
Introduction to Logic by Irving Marmer Copi.
Essay Concerning Human Understanding Book IV – John Locke

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Basic argument

Matters of confusion

Contraposition and Transposition

Absence of evidence

Evidence of absence

Negative evidence

Null result

Argument from incredulity/Lack of imagination

Argument from self-knowing (auto-epistemic)

Distinguishing absence of evidence from evidence of absence

Formal argument

Absence of evidence

Negative results

Evidence of absence

Arguments from ignorance

In the field of science

Principles in law

Origin of the term

Sources

See also

External links