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If someone wants to believe in leprechauns, they can avoid ever being proven wrong by using ad hoc hypotheses (e.g., by adding "they are invisible", then "their motives are complex", and so on).[1]

In science and philosophy, an ad hoc hypothesis is a hypothesis added to a theory in order to save it from being falsified. Often, ad hoc hypothesizing is employed to compensate for anomalies not anticipated by the theory in its unmodified form.


In the scientific communityEdit

Scientists are often skeptical of theories that rely on frequent, unsupported adjustments to sustain them. This is because, if a theorist so chooses, there is no limit to the number of ad hoc hypotheses that they could add. Thus the theory becomes more and more complex, but is never falsified. This is often at a cost to the theory's predictive power, however.[1] Ad hoc hypotheses are often characteristic of pseudoscientific subjects.[2]


Embryos of falsifiable hypotheses and theoriesEdit

An ad hoc hypothesis is not necessarily incorrect; in some cases, a minor change to a theory was all that was necessary. For example, Albert Einstein's addition of the cosmological constant to general relativity in order to allow a static universe was ad hoc. Although he later referred to it as his "greatest blunder", it may correspond to theories of dark energy.[3]

Mislabelling criticism of methodology as ad hocEdit

The assumption that people are prone to make up ad hoc hypotheses to defend their world views is criticized by a number of historians of science and philosophers of science as it can lead to allegations of any valid criticism being an attempt to justify a specific theory that is not there. Such allegations can stand in the way of important criticism of flawed methodologies, thus causing the flawed methods to remain in continued use, by allegations that anyone who points out flaws in the methods are doing it to defend a purported worldview. The allegations are made unfalsifiable and unable to self-correct by explaining away any criticism of the allegations as rationalization or self-deception. The problem includes false dichotomies that claim there is a face-off between two world views, missing the point that any number of hypotheses and theories make some predictions that incidentally overlap with predictions made by other hypotheses or theories while also making some unique predictions (e.g. a partial incidental overlap but also key differences of predictions between the obsolete luminiferous aether theory and the modern vacuum energy theory that make the evidence that falsify the former fall outside the predictions made by the latter) which is often confused by "ad hoc" allegers with one hypothesis being a "justification" for another hypothesis with different predictions. False dichotomies cause not only allegations against hypotheses and theories but also against general remarks of flawed methodologies that suggest no specific hypotheses or theories that can dismiss remarks of technical errors in the equipment, remarks of statistical confirmation biases that are due to institutional publication bias between "ordinary claims" and "extraordinary claims" rather than individual brains, remarks of biased searching for other explanations in some cases but not others that lead to false appearances of a phenomenon "really" existing in one group but not in another, and other types of methodological errors. By arguing that a diversity of hypotheses and theories until falsification enhances the possibility that one correct one survives future falsification attempts, the distinction between "claimant" individuals and "non-claimant" institutions implicit in the concept of burden of proof is criticized for not being evidence-based and that the same empirical data can falsify many hypotheses and theories with overlapping predictions without the expensive separate testing of each hypothesis that is alleged when claiming that "most hypotheses must be ignored to save money".[4][5]

Gaps in knowledge and unclear observationsEdit

Naturally, some gaps in knowledge, and even some observations that contradict a theory, must be temporarily tolerated while research continues. To temper ad hoc hypothesizing in science, common practice includes falsificationism (somewhat in the philosophy of Occam's razor). Falsificationism means scientists become more likely to reject a theory as it becomes increasingly burdened by ignored contradicting observations, and by ad hoc hypotheses.

See alsoEdit


  1. ^ a b Stanovich, Keith E. (2007). How to Think Straight About Psychology. Boston: Pearson Education. Pages 19-33
  2. ^ Carroll, Robert T. "Ad hoc hypothesis." The Skeptic's Dictionary. 22 Jun. 2008 <>.
  3. ^ Texas A&M University. "Einstein's Biggest Blunder? Dark Energy May Be Consistent With Cosmological Constant." ScienceDaily 28 November 2007. 22 June 2008 <>.
  4. ^ Joseph Agassi, Abraham Meidan (2016) "Beg to Differ: The Logic of Disputes and Argumentation"
  5. ^ R. W. Home (2013) "Science under Scrutiny: The Place of History and Philosophy of Science"

External linksEdit