View source for Module:Explanatory power

{{Short description|Ability of a theory to explain a subject}}
{{about|explanatory power in the context of the philosophy of science|a statistical measure of explanatory power|coefficient of determination|and|mean squared prediction error}}
{{refimprove|date=October 2016}}

'''Explanatory power''' is the ability of a [[hypothesis]] or [[theory]] to explain the subject matter effectively to which it pertains. Its opposite is ''explanatory impotence''.

In the past, various criteria or measures for explanatory power have been proposed. In particular, one hypothesis, theory, or explanation can be said to have more explanatory power than another about the same subject matter{{cn|date=November 2021}}

* If more facts or observations are accounted for;
* If it changes more "surprising facts"  into "a matter of course" (following [[Charles Sanders Peirce#Modes of inference|Peirce]]);
* If more details of causal relations are provided, leading to a high [[accuracy and precision]] of the description;
* If it offers greater [[predictive power]] (if it offers more details about what should be expected to be seen and not seen);
* If it depends less on authorities and more on observations;
* If it makes fewer assumptions;
* If it is more [[falsifiable]] (more [[testable]] by observation or experiment, according to [[Karl Popper|Popper]]).
* If it can be used to compress encoded observations into fewer bits ([[Solomonoff's theory of inductive inference]])

Recently, [[David Deutsch]] proposed that theorists should seek explanations that are ''hard to vary''. A theory or explanation is hard to vary if all details play a functional role, i.e., cannot be varied or removed without changing the predictions of the theory. Easy to vary (i.e., bad) explanations, in contrast, can be varied to be reconciled with new observations because they are barely connected to the details of the phenomenon of question.

==Examples==
Deutsch takes examples from [[Greek mythology]]. He describes how very specific, and even somewhat falsifiable theories were provided to explain how the god [[Demeter]]'s sadness caused the seasons. Alternatively, Deutsch points out, one could have just as easily explained the seasons as resulting from the god's happiness, which would make it a poor explanation because it is so easy to arbitrarily change details.<ref name=DeutschTED>[http://www.ted.com/talks/david_deutsch_a_new_way_to_explain_explanation.html David Deutsch, "A new way of explaining explanation"]</ref> Without Deutsch's criterion, the 'Greek gods explanation' could have just kept adding justifications. The same criterion, of being "hard to vary", may be what makes the modern explanation for the [[seasons]] a good one. None of the details about the earth rotating around the sun at a certain angle in a certain orbit can be easily modified without changing the theory's coherence.<ref name=DeutschTED/><ref>David Deutsch (2011), [[The Beginning of Infinity|The Beginning Of Infinity"]], ch1, The Reach of Explanations</ref>

==Relation to other criteria==
The philosopher Karl Popper acknowledged it is logically possible to avoid falsification of a hypothesis by changing details to avoid any criticism, adopting the term an ''[[immunizing stratagem]]'' from [[Hans Albert]].<ref>Ray S. Percival (2012), ''The Myth of the Closed Mind: Explaining why and how People are Rational'', p.206, Chicago.</ref> Popper argued that scientific hypotheses should be subjected to methodological testing to select for the strongest hypothesis.<ref>Karl R. Popper (1934), ''The Logic of Scientific Discovery'', p.20, Routledge Classics (ed. 2004)</ref>

==See also==
* [[Falsifiability]]
* [[Razor (philosophy)]]
* [[Critical Rationalism]]

==References==
{{Reflist}}

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