World Library  
Flag as Inappropriate
Email this Article

Existential fallacy

Article Id: WHEBN0000705934
Reproduction Date:

Title: Existential fallacy  
Author: World Heritage Encyclopedia
Language: English
Subject: List of fallacies, Formal fallacy, Affirmative conclusion from a negative premise, Affirming a disjunct, Illicit minor
Collection: Quantificational Fallacies, Syllogistic Fallacies
Publisher: World Heritage Encyclopedia

Existential fallacy

The existential fallacy, or existential instantiation, is a formal fallacy. In the existential fallacy, we presuppose that a class has members when we are not supposed to do so; that is, when we should not assume existential import.

One example would be: "Every unicorn definitely has a horn on its forehead". It does not imply that there any unicorns at all in the world, and thus it cannot be assumed that, if the statement is true, somewhere there is a unicorn in the world (with a horn on its forehead). The statement, if assumed true, only implies that if there were any unicorns, each would definitely have a horn on its forehead.

An existential fallacy is committed in a medieval categorical syllogism because it has two universal premises and a particular conclusion with no assumption that at least one member of the class exists, which is not established by the premises.

In modern logic, the presupposition that a class has members is seen as unacceptable. In 1905, Bertrand Russell wrote an essay entitled "The Existential Import of Proposition", in which he called this Boolean approach "Peano's interpretation".

The fallacy does not occur in enthymemes, where hidden premises required to make the syllogism valid assume the existence of at least one member of the class .

One central concern of the Aristotelian tradition in logic is the theory of the categorical syllogism. This is the theory of two-premised arguments in which the premises and conclusion share three terms among them, with each proposition containing two of them. It is distinctive of this enterprise that everybody agrees on which syllogisms are valid. The theory of the syllogism partly constrains the interpretation of the forms. For example, it determines that the A form has existential import, at least if the I form does. For one of the valid patterns (Darapti) is:
Every C is B
Every C is A
So, some A is B
This is invalid if the A form lacks existential import, and valid if it has existential import. It is held to be valid, and so we know how the A form is to be interpreted. One then naturally asks about the O form; what do the syllogisms tell us about it? The answer is that they tell us nothing. This is because Aristotle did not discuss weakened forms of syllogisms, in which one concludes a particular proposition when one could already conclude the corresponding universal. For example, he does not mention the form:
No C is B
Every A is C
So, some A is not B
If people had thoughtfully taken sides for or against the validity of this form, that would clearly be relevant to the understanding of the O form. But the weakened forms were typically ignored.[1]
— Terence Parsons, The Stanford Encyclopedia of Philosophy

See also


  1. ^ Parsons, Terence (2012). "The Traditional Square of Opposition". In Edward N. Zalta. The Stanford Encyclopedia of Philosophy (Fall 2012 ed.). 3-4. 

External links

  • Fallacy files: existential fallacy
  • FOLDOC: existential fallacy

This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.