masked man fallacy

English

Alternative forms

• masked-man fallacy

Noun

masked man fallacy (plural masked man fallacies)

1. (logic, philosophy) A fallacy of inferring that since one knows (or does not know) something by one description, one must know (or not know) it by another, as in "I know who my father is. I do not know who the masked man is. Therefore, my father is not the masked man."
   • 1978, Bernard Williams, Descartes: The Project of Pure Enquiry, New York: Routledge, published 2005, page 97:

     That is to say, one cannot infer from one's subjective state of certainty and uncertainty about two propositions, to the objective connection or lack of connection between them; but it is just such an inference that Descartes seems to be making about himself and his body, and which gives his argument its embarrassing resemblance to the masked man fallacy.

   • 1999, Jonathan E. Pike, From Aristotle to Marx: Aristotelianism in Marxist social ontology‎^[1], Ashgate, page 176:

     Consider the Masked Man fallacy, which shows that I can know something under one description but not under another.

   • 2001, Reports of the Tax Court of the United States‎^[2], volume 117:

     […] that because the per diem payments are compensatory, ipso facto they are not travel expenses. Without further explication, this latter proposition might be thought to exemplify a species of the so-called masked man fallacy ("I know who my father is; I do not know who the masked man is; so, my father is not the masked man.").

Synonyms

• intensional fallacy

See also

• identity of indiscernibles, Leibniz's law

Further reading

• masked man fallacy on Wikipedia.Wikipedia