Negative evidence

{{lognav}}{{hatnote|Not to be confused with the [[argument from ignorance]], where the '''lack of evidence''' for something is considered to be '''evidence for''' the same.}}

'''Negative evidence''' denotes a failed necessary prediction of a theory, which thus counts as [[evidence]] ''against'' said theory.<ref group=note>Note that this negative evidence does not ''support'' any rival theories ''per se'', it just means that ''the theory being tested'' failed to line up with reality.</ref> Negative evidence is produced when any given theory by necessity predicts something specific which, upon closer inspection, fails to materialize. Any general theory must [[Hindsight bias|not just]] explain ''the past'' and ''present'', but also make accurate ''predictions'' about where to look or what will happen [[Falsifiability|that can be tested]]. Absence of something predicted by the theory in question (the "negative" evidence) thus suggests that the theory is mistaken.

Negative evidence should not be confused with the discovery of novel evidence ''not predicted'' (or even considered) by an existing theory. Instead, negative evidence results from the ''[[reductio ad absurdum]]'', meaning; when something that would ''have'' to be true — based on a supposed theory — turns out ''not'' to be.

==Form==
{{syl
|2=If '''X''', then ''always'' '''Y'''.
|4=Not '''Y'''.
|5=C|6=Not '''X'''.
}}

==In science==
In order for a prospective theory to be [[falsifiable]], and thus qualify as sound [[science]], [[hypotheses]] must propose testable predictions in the observable world. Then, one does the experiment and sees whether the prediction comes true.

Essentially, negative evidence is considered found when no positive evidence could be located when and where the theory being tested ''predicts'' that such positive evidence would need to be.

For example, [[evolutionary theory]] predicts that a dynamic environment causes new [[species]] to evolve via a [[Natural selection|natural process of selection and adaptation]], branching them out from their respective ancestor species into various new forms of [[life]].

If the ground had contained billion-year old [[fossil]]s of [[Human–dinosaur coexistence|anatomically modern humans right next to fossils of triceratopses]], trilobites and [[Dog|golden retrievers]] of the same age and strata, [[Darwinism]] would be in trouble.

Thankfully, this turned out not to be the case — [[Transitional fossil|every adaption appears at the right time and place in the geological timeline]] — and so, another test  was passed by [[evolutionary theory]].

==Methods==
An absence of something can be proved in various ways, e.g., by a ''reductio ad absurdum'' or by proving something else that is inconsistent with the presence of that something (a very useful approach known in [[mathematics]] as proof by contradiction. For example, in [[law]], a party may have the burden of proving nonreceipt of certain correspondence and may bear that burden of proof (at least by a preponderance of the evidence) by introducing into evidence a docket record in which the correspondence would have been noted. In mathematics, there are plenty of proofs of negative propositions, such as "there is no largest prime number"<ref>{{wpa|Euclid's theorem}}</ref> or "there is no rational square root of 2".<ref>{{wpa|Square root of 2}}</ref>

Proving a negative is often harder than proving a positive.

==Examples==
If your neighbor claimed that teenagers were racing their cars outside of his house, the absence of teenagers, cars, and tire marks on the street would be negative evidence against his claim.

The [[problem of evil]] convinces [[Richard Carrier]] that an [[Omniscience|omniscient]], [[Omnipotence|omnipotent]], and [[Omnibenevolence|omnibenevolent]] (OOO) [[god]] is extremely unlikely. This is because, if an OOO god existed, then [[evil]] should not exist. Evil does exist. Ergo (thinks Carrier) an OOO god likely does not.<ref>[http://infidels.org/library/modern/richard_carrier/theory.html Proving a Negative] [[Richard Carrier]] (1999)</ref>

==Fallacy==
{{cquote|Contradiction is not a sign of falsity, nor the lack of contradiction a sign of truth.|||Blaise Pascal<ref>https://www.brainyquote.com/quotes/quotes/b/blaisepasc132582.html</ref>}}
Taken too far, negative evidence becomes an [[argument from ignorance|appeal to ignorance]], the mistake of believing that because we have not (yet) found evidence, it must not exist.

Negative evidence occurs when an absence of evidence is ''actively'' found when ''actively'' looking for something. (Don't see your [[car]] in the garage? It's probably not in the garage.) An appeal to ignorance occurs when an absence of evidence is found when nobody has done any looking! (Maybe you should actually walk into the garage and check, before assuming your car isn't there.)

Negative evidence is often used in this capacity by advocates of [[creationism]], whose proponents argue that we should have found more fossil evidence of [[Transitional fossil|intermediate species]] if evolution is correct.

==See also==
*[[Absence of evidence]]
*[[Shakespeare authorship]]
*[[Truther]]
*[[Burden of proof]]

==Notes==
{{reflist|group=note}}

==References==
{{reflist|2|80%}}

{{logfal}}

[[Category:Philosophy of science]]
[[Category:Science]]
[[Category:Valid logical methods]]

Categories: Philosophy of science, Science, Valid logical methods