PSA2016: The 25th Biennial Meeting of the Philosophy of Science Association

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The Severity Approach to Demarcation

Several recent treatments of the demarcation problem cast it as a problem of how to adjudicate between rationally acceptable and unacceptable methods and theories (e.g., Boudry 2013). One such approach, from Hansson (2013), involves reconceptualizing the relevant notion of science to cover any systemic area of study thought to offer the most reliable knowledge for its subject.

Hansson (2013, 70–71) provides a definition of pseudoscientific statements as statements that are part of a doctrine whose proponents create the appearance of being a science (broadly defined), that are also unacceptably unreliable. He argues that how we determine whether the statement is adequately reliable cannot be narrowed in a way that is useful for direct application, due to the lack of methodological uniformity across different branches of science (2013, 73–74).

I show that, as a result, Hansson’s definition fails to illuminate what it means to be pseudoscientific. I suggest a refinement to his proposal, and argue that the modified definition applies across sciences while providing insight into the status of particular experiments or research projects. Following Mayo (1996), I propose that the epistemological distinction between science and pseudoscience has to do with severe testing. I consider inquiries the fundamental subjects of scientific and pseudoscientific status, as opposed to statements, theories, or research programs. The methods and principles we call scientific are so because of their role in probative inquiry.

Pseudoscientific inquiries generate claims fitting a modified version of Hansson’s aforementioned definition. In the new definition, his criterion that the statement is unreliable is replaced with the criterion that the relevant inquiry fails a severity condition. This condition is that, before accepting a hypothesis H as the solution to a problem, the inquiry must subject it to severe testing (Mayo 1996, 277–278). A severe test is one where H would, with high probability, fail if it were false. For some investigations, ‘probability’ can be cashed out statistically, e.g., using error statistics; for other inquiries, a less formal notion will apply.

Pseudoscientific inquiries, on this account, suffer from a lack of severe testing. I show that this view can account for commonsense judgments about what counts as pseudoscientific, and that it can provide insight into attempts to discriminate which inquiries are scientific without falsely assuming methodological uniformity. Severe testing can take different forms: for example, a historical inquiry might demand probing for sources of error like unreliable source documents. Lastly, I explore consequences of this position, such as that it is mistaken to dismiss supernatural investigation as inherently pseudoscientific.


Boudry, Maarten. 2013. “Loki’s Wager and Laudan's Error.” In Philosophy of Pseudoscience : Reconsidering the Demarcation Problem, edited by Massimo Pigliucci and Maarten Boudry, 79-95. Chicago University Press.

Hansson, Sven Ove. 2013. “Defining Pseudoscience and Science.” In Philosophy of Pseudoscience : Reconsidering the Demarcation Problem, edited by Massimo Pigliucci and Maarten Boudry, Online, 61–75. Chicago University Press.

Mayo, Deborah G. 1996. “Ducks, Rabbits, and Normal Science: Recasting the Kuhn’s-Eye View of Popper's Demarcation of Science.” The British Society 47 (2): 271–90.

Author Information:

Jack Parker    
Carnegie Mellon University


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