Wrong disjunction

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The fallacy of imperfect disjunction (alternative terms see below) is a fallacy from an assumption of the form "either A or B (or C etc.)",

  1. where the possible alternatives are incomplete, d. H. still other cases are possible, and / or
  2. in which several alternatives can occur and the disjunction is therefore wrong.

definition

Gustav Adolf Lindner refers to the false conclusion by false disjunction as one of the three forms of fallacia falsi medii (dt. Surreptitiously ):

"3. By false disjunction , when the Disjunktionsreihe in the major, an incomplete is. If the indirect proof is based on such an incomplete, but considered to be complete, series of disjunctions, a false conclusion can be brought about if the disjunctive term that has been omitted is the one that applies in the present case. For example: This person is either a Christian or an atheist; Socrates was either an old citizen or a sophist. (Major clause in the evidence of Socrates' guilt). "

For Friedrich Ueberweg , too , the fallacy through false disjunction is a form of Fallacia falsi medii:

“The attempted proof from wrong premises is called fallacia falsi medii if the incorrectness lies in the connection of the middle term with the other terms . In the case of the indirect proof, of the inaccuracies in the premises, the most frequent and most disadvantageous is the incomplete , but wrongly considered to be complete, disjunction in the major . "

Since Lindner and Ueberweg, logic has changed dramatically. That is why today we call any conclusion in which one of the premises is a disjunction that is false, a fallacy due to false disjunction.

Even Hermann Lotze had another case in mind: the incomplete case distinction. If an assertion holds for every disjunction, then if the disjunction is complete, then it holds for every case. However, if there is a false disjunction, it may be that the assertion does not apply to an alternative that is missing in the disjunction.

NI Kondakow provides the following example of the fallacy due to incorrect disjunction:

Every chemical element is either solid or liquid.
Oxygen is not solid.
It follows: Oxygen is liquid.

The sentence is wrong because the first premise is incomplete because there are also gaseous elements.

Another example:

Animals are male or female.
This animal is not male.
It follows that this animal is female.

This example overlooks the fact that there are animals that have both sexes and others that are sexless.

This example shows that the disjunction can be wrong not only because it is incomplete, but also because several alternatives can appear together. Charles Gray Shaw counted this possibility as part of the fallacy.

Alternative names

Other terms are common for the fallacy. Jakob Friedrich Fries and Hermann Lotze speak of the incomplete disjunction . Others speak of the fallacy of the false alternative , Bifurkationsfehlschluss (Engl. Fallacy of bifurcation) or the Sherlock Holmes fallacy (Engl. Sherlock Holmes fallacy).

Special cases

Wrong dilemma

There is a false disjunction only two Disjunktionsgliedern is called a false dilemma or the either-or fallacy (Engl. Either / or fallacy).

All-or-nothing fallacy

A special case of the false dilemma is the all-or-nothing fallacy, also known as black-and-white fallacy. The two ends of a scale are made into disjunction. It is pretended that there are no intermediate forms. Something is strong or weak, good or bad, or black or white.

Example:

Either you want privacy or security.
You want security.
It follows from this: You don't want privacy.

Happy disjunction

In the case of a false disjunction, one can be lucky that although the disjunction is incomplete, the conclusion is still correct, since from false one can also infer the truth. This is referred to errors of happy disjunction (Engl. Mistake of lucky disjunction).

For example, the doctor cannot consider all possible causes of illness, but can have the actual causes in his perspective, if he then excludes all but one, and one is correct, then there is a happy disjunction.

Similar cases

Although the description will usually include examples that are exclusive ors, the same error will work with an inclusive ors.

Individual evidence

  1. ^ John Veitch: Institutes of logic . Edinburgh / London: Blackwood 1885, 536.
  2. ^ Gustav Adolf Lindner: Textbook of formal logic. For use in higher education institutions and for self-teaching . Vienna: Carl Gerold's Sohn 1867 (2nd edition), 231.
  3. ↑ Friedrich Ueberweg: System of logic and history of logical teachings . Bonn: Adolph Marcus 1868 (3rd edition), 403.
  4. ↑ cf. Hermann Lotze: Logic. Three books - on thinking, examining and knowing . Leipzig: Hirzel 1874, 332.
  5. ↑ NI Kondakow: Dictionary of Logic . Leipzig: Bibliographisches Institut 1983 (2nd edition), 157.
  6. ↑ Rick Hayes-Roth: Truthiness Fever. How Lies and Propaganda Are Poisoning Us and a Ten-Step Program for Recovery . Booklocker 2011, 76.
  7. ^ Charles Gray Shaw: Logic in Theory and Practice . Prentice-Hall 1935, 216.
  8. ↑ Jakob Friedrich Fries: System of Logic. A manual for teachers and for self-use . Heidelberg: Winter 1837 (3rd edition), 111.
  9. ^ Hermann Lotze: Logic. Three books - on thinking, examining and knowing . Leipzig: Hirzel 1874, 332.
  10. ↑ Thomas Wilhelm: Recognize and ward off manipulations. The training book. Heap, 168.
  11. ^ S. Morris Engel / Angelika Soldan / Kevin Durand: The Study of Philosophy . Lanham, Maryland: Rowman & Littlefield (6th ed.), 133.
  12. ↑ Stephen Law: Thinking Tools: The Sherlock Holmes Fallacy . Think (2008) 6, 219-221.
  13. ↑ David A. Hunter: A practical guide to critical thinking. Deciding what to do and believe . New Jersey: Wiley 2009, 151.
  14. ^ Gary L. Cesars: Either / Or Fallacy . In: John Lachs / Robert Talisse (eds.): American philosophy. To encyclopedia . New York: Routledge 2008, 217.
  15. ^ Daniel J. Solove: Nothing to Hide: The False Tradeoff Between Privacy and Security . Yale University Press 2011.
  16. ^ Douglas N. Walton: Argumentation schemes for presumptive reasoning , Mahwah, NJ: Lawrence Erlbaum Associates, 103.
  17. ^ Nancy M. Cavender / Howard Kahane: Logic and Contemporary Rhetoric. The use of reason in everyday life . Belmont, CA: Wadsworth 2010 (11th ed.), 58.
  18. ↑ cf. Daniel J. Solove: Nothing to Hide: The False Tradeoff Between Privacy and Security . Yale University Press 2011.
  19. ↑ David A. Hunter: A practical guide to critical thinking. Deciding what to do and believe . New Jersey: Wiley 2009, 153.