Argument from ignorance: Encyclopedia - Argument from ignorance

Argument from ignorance

The argument from ignorance, also known as argumentum ad ignorantiam or argument by lack of imagination, is the assertion that if something is currently inexplicable to some people, then it did not (or could not) happen, or that if evidence of something has not been scientifically proven to their satisfaction, then it cannot exist. "Absence of evidence is not evidence of absence" is an adage used to explain that one's own "ignorance" (or, one's "absence of evidence") does not disprove anything (or, "is not evidence of absence"). In other words, mere personal belief, poor logic, or closed-mindedness masquerading as certainty is not logical.

This is similar to (but not the same as) the Argument from Personal Incredulity (also known as Argument from Personal Belief or Argument from Personal Conviction), where a person asserts that because they personally find a premise unlikely or unbelieveable, it can be safely assumed not to be true.

In an Argument from Personal Incredulity or Argument from Ignorance, the speaker considers or asserts that something clearly proven to be accurate is nonetheless false, implausible, or not obvious to him personally (or that something clearly not proven to be accurate is nonetheless true); or he attributes such a belief to the world generally; examples of the above are, "It is hard to see how...," "I cannot understand how...," or "it is obvious that...". The speaker will sometimes continue by using this assertion, without any logical foundation or empirical evidence to support its validity, as a premise which then "evidences" and supports his conclusions, despite that it is merely an untested assertion which still needs its own evidence in order for any conclusions which are based upon it to be logically valid.

Many uses of the Argument from Ignorance are considered fallacious, especially in academic papers which are expected to be rigorous about their key premises and empirical foundations. However, in some cases (such as that which the noted author Irving Copli descibes below) where affirmative evidence could reasonably be expected to be found, but following careful unbiased examination, this evidence has still not been found, then it might become expedient, and sometimes even prudent, to infer that this might suggest (though it does not prove, logically) that the evidence does not exist. Or, where the speaker can reasonably assume that all sane people will agree with a premise (e.g. "The sky is blue"), then he might decide it is unnecessary to provide evidence supporting that assertion; however, this issue (which epistemological foundationalism is closely related to, and intertwined with) is still debated.

The types of fallacies noted above should not be confused with the reductio ad absurdum method of proof, in which a genuine logical contradiction of the form "A and not A" is used to disprove a premise.

Argument from ignorance - Description

Irving Copi writes that:

In addition, one might add a third case, the argument that something is false or true because the speaker cannot (or finds it hard to) conceive otherwise. This argument by lack of imagination is sometimes expressed in the form "Y is absurd (because I can not imagine it), therefore it must be untrue," or "It is hard to see how..." [ie I personally cannot see, or lack imagination, how], and is sometimes confused with the logically valid method of argument, reductio ad absurdum. A logical argument using reductio ad absurdum would be framed as "X logically leads to a probably impossible (absurd) conclusion, therefore it must be false." In reductio ad absurdum, it is necessary to show that X implies a contradiction (such as "not X", or "Y and not Y" for some other proposition Y). In an argument from ignorance, X implies something which the speaker considers absurd or implausible rather than something which the speaker can prove to be a contradiction.

Argument from personal incredulity is very similar, e.g. "I am unable to believe/understand X, therefore it must be false."

Argument from ignorance - Examples

• "I find it hard to imagine a way in which a thousand-ton piece of metal could fly through the air. Therefore, airplanes will never work." (This was a common argument why trains could never work, it was "obvious" that if one travelled fast, the air would be blown away too fast to breathe)
• "It is difficult to see how monkeys can be intelligent because they cannot speak." (Argument from personal belief: it may be difficult for the speaker. The fallacy is, perhaps it could be true despite how "difficult" it is for the speaker to believe. Or perhaps it is not difficult for some other experts to believe)
• "You can't prove your views, so don't argue with me!" (a common argument from ignorance - the fact that the other person may not be able to show evidence to 'prove' their side (in whatever way is demanded) does still not necessarily mean in the slightest that their view is wrong)
• In his book Probability of God, Bishop Hugh Montefiore casts doubt on neo-Darwinian evolution with the following statement: If polar bears are dominant in the Arctic, then there would seem to have been no need for them to evolve a white-coloured form of camouflage. This argument from lack of imagination was famously dismissed by the evolutionist Richard Dawkins, who wrote that if the writer had thought to imagine a black polar bear trying to sneak up on a seal in the arctic, he would see the evolutionary value of such fur.
• "The solar system must be younger than a million years because even if the sun was made of solid coal and oxygen it would have burned up within that time at the rate it generates heat" (an argument from ignorance, from 19th Century encyclopedias, based on the assumption that because there was no known means at that time of producing heat more efficient than coal, this logically put a limit on the Sun's possible age. In fact in the 20th Century with the discovery of radioactivity and nuclear fusion, the sun's age was more correctly dated at many billions of years old instead. The 'ignorance' in this case was the omission of considering whether there might be a more efficient generator of heat that has not yet been discovered, which had not been taken into account.)
• "This city can't handle public transportation because we don't have room for any train tracks." (the speaker fails to consider, or is ignorant of the possibility, that there might be other means of providing public transportation, such as buses, as well as the city's ability to appropriate land or excavate a tunnel, which would make it possible)

Argument from ignorance - Law

In most modern criminal legal systems, it is the responsibility of the prosecution to prove "beyond reasonable doubt" that the defendant is guilty. So in cases where the defendant has been acquitted, it is a logical fallacy to conclude that they were innocent - this would be to assume a proposition simply because it has not been proved false. The presumption of innocence is inspired by consideration for human rights, not by logical necessity.

(Note that in Scotland, unusually, a jury may also return a verdict "not proven", meaning that the prosecution has not proven guilt to the necessary standard but neither do they feel sufficiently certain that the defendant is innocent, which avoids this situation).

As another example, suppose someone were to argue:

• I cannot imagine any way for Michael Jackson to have slept with young boys without having sex with them.
• Therefore he must be guilty of the crime of statutory rape.

This would be an argument from lack of imagination, and is logically fallacious. Just because the person making the argument cannot imagine how this might have happened does not necessarily imply that their conclusion is correct - their imagination is, in this regard, lacking, because they cannot imagine the premise as being possible. (Neither, it should be noted, does it mean it is not correct. It simply means the person has an untested belief or opinion about it)

Outside criminal law, problems of ignorance or lack of evidence and information (by the court) are settled by rules regarding the standard of proof and burden of proof.

Argument from ignorance - Science

Unexplained phenomena are often an indication that a particular scientific theory is incomplete, or incorrect. For example, the wave theory of light does not explain the photoelectric effect, though it fits well with the results of the double-slit experiment. However, later theories based around quantum mechanics explain both. It would be a mistake to assert that because a phenomenon is unexplained by current scientific theories, it is unexplainable by science.

See also

• negative proof

Categories: Articles that need to be wikified | Logical fallacies

Adapted from the Wikipedia article "Argument from ignorance", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki