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pragmatic fallacy

The pragmatic fallacy is committed when one argues that something is true because it works and where 'works' means something like "I'm satisfied with it," "I feel better," "I find it beneficial, meaningful, or significant," or "It explains things for me." For example, many people claim that astrology works, numerology works, therapeutic touch works, or palmistry works. What 'works' means here is vague and ambiguous. At the least, it means that one perceives some practical benefit in believing that it is true, despite the fact that the utility of a belief is independent of its truth-value.

The pragmatic fallacy is common in "alternative" health claims and is often based on post hoc reasoning. For example, one has a sore back, wears the new magnetic or takionic belt, finds relief soon afterwards, and declares that the magic belt caused the pain to go away. How does one know this? Because it works!

There is a common retort to the skeptic who points out that customer satisfaction is irrelevant to whether the device, medicine, or therapy in question really is a significant causal factor in some outcome. Who cares why it works as long as it works? You can argue about the theory as to why it works, but you can't argue about the customer satisfaction. They feel better after using the product. That's all that matters.

It isn't all that matters. Testimonials are not a substitute for scientific studies, which are done to make sure that we are not deceiving ourselves about what appears to be true. It is especially necessary to do controlled studies of alleged pain relievers to avoid self-deception due to the placebo effect,  post hoc reasoning, or the regressive fallacy. We may not want to question too deeply the felt relief, but we must question the cause of that relief.

It is easy to understand why someone with "terminal" cancer who seeks out an "alternative" treatment and finds the cancer goes into remission soon afterwards would attribute miraculous causal efficacy to the "alternative" treatment. However, if the "alternative" treatment is not really the cause of the remission, then others who seek the treatment will be filled with false hope. Of course, those patients who try the same treatment but who die anyway are not around to tell their story. Their surviving loved ones may even claim that the only reason the treatment did not work was because the patient came to it too late. The only way to know for sure whether the treatment has causal efficacy is to study its application under controlled conditions. Testimonials regarding how well the treatment works may be heartfelt, but they can be dangerously misleading.

post hoc fallacy

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