Appeal to probability

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An appeal to probability (or appeal to possibility, also known as possibiliter ergo probabiliter, "possibly, therefore probably") is the logical fallacy of taking something for granted because it would probably be the case (or might possibly be the case).[1][2] Inductive arguments lack deductive validity and must therefore be asserted or denied in the premises. A mere possibility does not correlate with a probability, and a mere probability does not correlate to a certainty, nor is just any probability that something happened or will happen sufficient to qualify as knowing that it did or will happen.

The fallacy could be understood as confusing likelihood(The probability of something is non-zero, usually large) with certainty(The probability of something is 1). E.g., For some event X, If Pr(X) > 0 then Pr(X) = 1. Using probabilistic arguments are not in and of themselves fallacious but concluding the conclusion follows logically rather than probabilistically is. When a probabilistic argument is made one must generally make it well understood that the argument itself is probabilistic based and hence the conclusion is probabilistic. Probabilistic arguments are generally transitive in nature and one must be careful when mixing logical and probabilistic arguments as to not to conclude something is logically true from a probabilistic argument.


A fallacious appeal to possibility:

Something can go wrong (premise).
Therefore, something will go wrong (invalid conclusion).
If I do not bring my umbrella (premise)
It will rain. (invalid conclusion).

Murphy's law is a (typically deliberate, tongue-in-cheek) invocation of the fallacy.




  • Bennett, Bo, "Appeal to possibility", Logically Fallacious, retrieved 13 March 2021
  • Carrier, Richard (2012), Proving History: Bayes's Theorem and the Quest for the Historical Jesus, Prometheus Books, p. 26-29, ISBN 9781616145590