Changes

==Fallacies of Presumption==

==Fallacies of Presumption==

Fallacies of presumption are fallacies in which an unstated or shaky presumption is made.

Fallacies of presumption are fallacies in which an unstated or shaky presumption is made.

===Contradiction===

===Contradiction===

A [[contradiction]] is a statement that contradicts its own terms. [[Aristotle]] famously stated that contradictions cannot exist. In any case of a contradition, some of the premises must be false.

:''Main article: [[Contradiction]]''

Contradictions normally form part of a proof by ''exclusion''. But contradictory arguments are some of the most common flawed arguments, and are closely akin to double standards (see above).

A contradiction is a statement that contradicts its own terms. [[Aristotle]] famously stated that contradictions cannot exist. In any case of a contradition, some of the premises must be false. A contradiction follows the form:

 

===Loaded question===

===Loaded question===

: ''Main Article: [[Loaded question]]''

: ''Main Article: [[Loaded question]]''

A [[loaded question]] is a question that assumes facts, usually unflattering, that are not in evidence, with the intent of trapping the other person into admitting those facts. The classic loaded-question example is "When did you stop beating your wife?" Another example is, "Do you disbelieve in [[global warming]], which 99.9 percent of all reputable scientists now accept?" (It is also an example of proof by numbers of adherents.)

A [[loaded question]] is a question that assumes facts, usually unflattering, that are not in evidence, with the intent of trapping the other person into admitting those facts. The classic loaded-question example is "When did you stop beating your wife?" Another example is, "Do you disbelieve in [[global warming]], which 99.9 percent of all reputable scientists now accept?"

===Proof by assertion===

===Proof by assertion===

An argument that states something as true without offering supporting evidence or attempting to construct a valid argument. The typical form of this "argument" is the "conclusion" of a [[non sequitur]].

An argument that states something as true without offering supporting evidence or attempting to construct a valid argument. This form of argument follows the form:

 

*P is true

 

Often the argument is simply repeated over and over, and no evidence for support is given.

 

Proof by assertion can also be broken down into several subcategories of fallacies: circular reasoning, manufactuing facts from a theory, and your theory does not work under my theory, so your theory must be wrong.

 

:''Main article: [[Circular reasoning]]''

[[Circular reasoning]], also called begging the question (Lat: petitio principii), is a form of proof by assertion in which one asserts a premise, then asserts a conclusion from that premise (directly or indirectly), and then tries to show that the last conclusion ''supports'' the original premise.

[[Circular reasoning]] is a form of proof-by-assertion in which one asserts a premise, then asserts a conclusion from that premise (directly or indirectly), and then tries to show that the last conclusion ''supports'' the original premise.

===Manufacturing facts from a theory===

====Manufacturing facts from a theory====

The assertion as fact of an undemonstrated, unobserved idea for no better reason than that a given theory requires that fact. We deal here with the assumption of a fact ''not in evidence.'' In the early stages of formulating a model, this sort of behavior is acceptable. But when repeated efforts to demonstrate such a new fact ''have failed'', the proper logical response is to discard or revise the theory, and not merely to assume that the "fact" still exists and "someone hasn't tried hard enough" to find it. This is ''especially'' true when someone develops evidence that the inferred "fact" ''could not possibly exist.''

Manufacturing facts from a theory is the assertion as fact of an undemonstrated, unobserved idea for no better reason than that a given theory requires that fact.

This is yet another form of proof-by-assertion, and is the source of many controversies in modern [[astronomy]], some of them strikingly bitter.

In the early stages of formulating a model, this sort of behavior is acceptable. But when repeated efforts to demonstrate such a new fact have failed, the proper logical response is to discard or revise the theory, and not merely to assume that the "fact" still exists and someone hasn't tried hard enough to find it. This is especially true when someone develops evidence that the inferred "fact" could not possibly exist.

====Your theory does not work under my theory, so your theory must be wrong====

====Your theory does not work under my theory, so your theory must be wrong====

: ''Main article: [[Your theory does not work under my theory, so your theory must be wrong]]''

: ''Main article: [[Your theory does not work under my theory, so your theory must be wrong]]''

The judgment of a theory by the premises and assumptions of another theory, rather than against its own premises and assumptions. This is a variation on proof-by-assertion.

This is fallacious reasoning, because there is no way to know ''why'' person A believes what he does, and Person B has used one reason which suits his own purpose. For example, it's quite possible that Person A wants to cut the program because he wants to change the funding to something which he thinks does a ''better'' job at defending the country.

===Tautology===

===Tautology===