Fallacy

Sources: www.wikipedia.com, www.nizkor.org, www.fallacyfiles.com

What is a FALLACY?
Ø A fallacy is a kind of error in reasoning. It differs from a factual error, which is simply being wrong about the facts. It is an "argument" in which the premises given for the conclusion do not provide the needed degree of support.
Ø It may convince others but is not logically sound. Though it should not be persuasive, it often is.
Ø It can be created unintentionally, or it may be created intentionally in order to deceive other people.
Ø A vast majority of the commonly identified fallacies involve arguments, although some involve explanations, or definitions, or other products of reasoning.
Ø It is a term used even more broadly to indicate any false belief or cause of a false belief.
Ø It should be noted that the truth of the conclusions of an argument does not determine whether the argument is a fallacy - it is the argument which is incorrect.
Fallacies can be categorized in a number of ways including:
Ø Formal (or Logical) fallacy versus Informal fallacy
A formal fallacy relies on a logical step in a proof or argument which is incorrect allowing a conclusion to be reached. It is one which involves an error in the form, arrangement or technical structure of an argument. It is therefore an invalid argument — argument where the concluding statement does not necessarily follow from the statements preceding it. The concluding statement may actually be objectively true, but it's truth does not depend on or follow from the other statements.
While a formal fallacy is invalid in form, an informal fallacy is a matter of unclear expression. A formal fallacy deals with the logic of the technical structure, while an informal fallacy deals with the logic of the meaning of language. The word "informal" does not here mean it is inferior, casual or improper. It only means that our focus is not on the form of the argument, but on the meaning of the argument. An informal fallacy involves such things as: the misuse of language — words or grammar, misstatements of fact or opinion, misconceptions due to underlying presuppositions, or just plain illogical sequences of thought.
Unlike a formal fallacy, an informal fallacy cannot be reduced to symbolic formulas. It however has characteristic profiles which can be arranged into the following general categories:
Ø Verbal fallacy
Verbal Fallacy uses some property of language, such as its ambiguity or length to mislead. It is one which a conclusion is obtained by improper or ambiguous use of words. It is generally classified as follows.
Equivocation consists in employing the same word in two or more senses, e.g. in a syllogism, the middle term being used in one sense in the major and another in the minor premise, so that in fact there are four not three terms ("All heavy things have a great mass; this is heavy fog; therefore this fog has a great mass.")
Connotation fallacies occur when a dysphemistic word is substituted for the speaker's actual quote and used to discredit the argument. It is a form of attribution fallacy.
Amphibology is the result of ambiguity of grammatical structure, e.g. of the position of the adverb "only" in careless writers ("He only said that," in which sentence, the adverb has been intended to qualify any one of the other three words).
Fallacy of Composition "From Each to All". Arguing from some property of constituent parts, to the conclusion that the composite item has that property e.g. "all the band members (constituent parts) are highly skilled, therefore the band (composite item) is highly skilled". This can be acceptable (i.e., not a fallacy) with certain arguments such as spatial arguments e.g. "all the parts of the car are in the garage, therefore the car is in the garage"
Division, the converse of the preceding, arguing from a property of the whole, to each constituent part e.g. "the university (the whole) is 700 years old, therefore, all the staff (each part) are 700 years old".
Proof by verbosity, sometimes colloquially referred to as argumentum verbosium - a rhetorical technique that tries to persuade by overwhelming those considering an argument with such a volume of material that the argument sounds plausible, superficially appears to be well-researched, and it is so laborious to untangle and check supporting facts that the argument might be allowed to slide by unchallenged.
Accent, which occurs only in speaking and consists of emphasizing the wrong word in a sentence. e.g., "He is a fairly good pianist," according to the emphasis on the words, may imply praise of a beginner's progress, or an expert's deprecation of a popular hero, or it may imply that the person in question is a deplorable pianist.
Figure of Speech, the confusion between the metaphorical and ordinary uses of a word or phrase.
Fallacy of Misplaced Concretion, identified by Whitehead in his discussion of metaphysics, this refers to the reification of concepts which exist only in discourse.
Ø Material fallacy
The taxonomy of material fallacies widely adopted by modern logicians is as follows:
Fallacy of Accident (also called destroying the exception or a dicto simpliciter ad dictum secundum quid)--makes a generalization that disregards exceptions (e.g., Cutting people is a crime. Surgeons cut people. Therefore, surgeons are criminals.)
Converse Fallacy of Accident (also called reverse accident, destroying the exception, or a dicto secundum quid ad dictum simpliciter)--argues from a special case to a general rule (e.g., Every swan I have seen is white, so it must be true that all swans are white.)
· Irrelevant Conclusion (also called Ignoratio Elenchi)--diverts attention away from a fact in dispute rather than address it directly. This is sometimes referred to as a "red herring". Subsets include:
purely personal considerations (argumentum ad hominem),
popular sentiment (argumentum ad populum--appeal to the majority; appeal to loyalty.),
fear (argumentum ad baculum),
conventional propriety (argumentum ad verecundiam--appeal to authority)
Affirming the Consequent--draws a conclusion from premises that do not support that conclusion by assuming Q implies P on the basis that P implies Q (e.g., If a person runs barefoot, then his feet hurt. Socrates' feet hurt. Therefore, Socrates ran barefoot. Other things, such as tight sandals, can result in sore feet.)
Denying the antecedent--draws a conclusion from premises that do not support that conclusion by assuming Not P implies Not Q on the basis that P implies Q (e.g., If I have the flu, then I have a sore throat. I do not have the flu. Therefore, I do not have a sore throat. Other illnesses may cause sore throat.)
Begging the question (also called Petitio Principii, Circulus in Probando--arguing in a circle, or assuming the answer)--demonstrates a conclusion by means of premises that assume that conclusion (e.g., Paul must be telling the truth, because I have heard him say the same thing many times before. Paul may be consistent in what he says, but he may have been lying the whole time.)
Fallacy of False Cause or Non Sequitur (Latin for "it does not follow")--incorrectly assumes one thing is the cause of another (e.g., Our nation will prevail because God is great.)
A special case of this fallacy also goes by the Latin term post hoc ergo propter hoc--the fallacy of believing that temporal succession implies a causal relation.
Another special case is given by the Latin term cum hoc ergo propter hoc -- the fallacy of believing that happenstance implies causal relation (aka as fallacy of causation versus correlation: assumes that correlation implies causation).
Fallacy of Many Questions (Plurium Interrogationum)--groups more than one question in the form of a single question (e.g., Is it true that you no longer beat your wife? A yes or no answer will still be an admission of guilt to wife-beating.)
Ø Deductive fallacy
In philosophy, the term logical fallacy properly refers to a formal fallacy : a flaw in the structure of a deductive argument which renders the argument invalid. It is often used more generally in informal discourse to mean an argument which is problematic for any reason, and thus encompasses informal fallacies as well as formal fallacies. – valid but unsound claims or bad nondeductive argumentation – .
The presence of a formal fallacy in a deductive argument does not imply anything about the argument's premises or its conclusion. Both may actually be true, or even more probable as a result of the argument (e.g. appeal to authority), but the deductive argument is still invalid because the conclusion does not follow from the premises in the manner described. By extension, an argument can contain a formal fallacy even if the argument is not a deductive one; for instance an inductive argument that incorrectly applies principles of probability or causality can be said to commit a formal fallacy.