Tag Archive | Ad Hoc Hypothesis

Project Logicality | Special Pleading

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Special Pleading, known loosely as ‘covering your ass,’ is the making of excuses, euphemistically called ‘reasons’ by those prone to invoke them, also as the ad hoc (or ‘in this’) hypothesis, the fallacy of limited scope, and if invented after the fact, post-hoc reasoning.

It often attempts to ‘explain’ special reasons or invoke presumed special cases for disproven claims no matter the logic or evidence against them.

It’s used to dismiss a question, argument, explanation, or lack of evidence as somehow and uniquely not applying to the claim to be rescued. Such special reasons are invariably offered without justification themselves.

I took the paranormal challenge, but I failed it because I was overwhelmed by the negative vibrations in the room, which scrambled my powers.


The Earth is flat. Ships only seem to go over the horizon because light travels in curves, not straight lines, to ordinary sight.


I failed the job interview because the stars weren’t right.


The classroom pixies weren’t favorable to my passing the exam.


I couldn’t complete the preliminary trial because the guy conducting it was a magician who cheated by using sleight of hand.


I couldn’t get a ‘hit’ during the remote viewing experiment because the target images didn’t have a single, distinct, easily visualized* feature to to focus on.

*read, “easily guessed.”

On that last: Remote viewing is supposed to be myopic? Never mind…

This is prevalent in parapsychology with what’s dubbed by a few very ticked-off parapsychologists the Wiseman Effect (after social psychologist Richard Wiseman. I wish I was notorious enough to have a logical fallacy named after me!) where disbelief, even accusations of repressed disbelief in neutral experimenters, is said to produce an effect cancelling psi-ability in a laboratory demonstration.

How can proponents of psi lose? After all, if you get positive results, they’re due to a psychic effect, and if you don’t they’re still due to a psychic effect! How can you test that by itself to know if there’s anything really going on? (answer: you can’t)

I’m going to steal from myself here, with something from one of my older posts on this blog:

There really are pixies playing in my garden, but you can’t see them because they’re shy and don’t want you to see them, magically invisible to both optical and infrared light, and can’t be made visible by sprinkling stuff on them because they’re also intangible at will, and oh, did I also mention that you can’t hear them because they’re supernaturally silent whenever they feel like it?

Special pleading can be carried to ridiculous lengths, grossly disregarding the rule of thumb known as Occam’s razor, in which smaller leaps of logic are considered preferable to great ones, and fewer assumptions are better than more. Or more to the point, those assumptions that are not beyond the plausible ability of the evidence to support them.

Any argument using this fallacy is thus rendered both unfalsifiable and unprovable in any meaningful sense. Ideas in science should be framed in testable form, or they are not science. It does no good to say “You can’t judge my claim because of special reasons X, Y, and Z that I just made up.”

Nor will it do to give any other arbitrary excuses why something can’t be tested. There’s a phrase for such ideas, I believe the highest form of scientific criticism, and it is “not even wrong.”

Science is messy, complex, and riddled with error, but that’s a strength with its built-in means of self-correction: there are times when a theory and its attendant hypotheses need refining to better conform to the data. This is not the use of post hoc reasoning: the amendments made here are those hypotheses that can be tested independently of their theory, and are those factors which are known to separately exist, have been observed directly or inferred from indirect observation.

It’s not a Good Idea™ to come up with not only untestable, but irrelevant reasons to prop up an idea failing the test of observation, the test of explanation, and the test of prediction, when it has no proverbial leg to stand on.

Tf. Tk. Tts.

(Last Update: 2017.06.06)