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([[Latin]]: "Argument directed toward the man"); An argument that attacks the character of one holding a contrary view, rather than attacking the view itself. ''Name-calling'' is a particularly crude form of this fallacy. ''Argumentum ad hominem'' is usually an attempt to accuse the other person of lying without saying so directly, or saying that his premises are somehow incompetent, irrelevant, or immaterial, or simply unreliable because they are self-serving. However, this is not good logic. If one suspects another of lying, then one should attempt to disprove the premises. One can raise a ''suspicion'' of deliberate falsehood on the part of another who has offered deliberate falsehood in the past. But the most that that can accomplish is to suggest that the other person's premises are unreliable and therefore require third-party corroboration.
([[Latin]]: "Argument directed toward the man"); An argument that attacks the character of one holding a contrary view, rather than attacking the view itself. ''Name-calling'' is a particularly crude form of this fallacy. ''Argumentum ad hominem'' is usually an attempt to accuse the other person of lying without saying so directly, or saying that his premises are somehow incompetent, irrelevant, or immaterial, or simply unreliable because they are self-serving. However, this is not good logic. If one suspects another of lying, then one should attempt to disprove the premises. One can raise a ''suspicion'' of deliberate falsehood on the part of another who has offered deliberate falsehood in the past. But the most that that can accomplish is to suggest that the other person's premises are unreliable and therefore require third-party corroboration.
===Genetic fallacy===
In general, this is the attempt to aver (that is, assert as true) or reject a theory by citing its origins as either reputable or disreputable. The usual expression of this fallacy is "Consider the source!" Thus it becomes a form either of ''argumentum ab auctoritate'' or of ''argumentum ad hominem'', depending on whether one seeks to verify or disprove the theory by this method.
When the origin of ''evidence'' or of ''premises'' is relevant to the reliability of the same, then asking a hearer to "consider the source" is valid. Judges in courts of [[law]], for example, routinely reject as unreliable the testimony of any witness who has demonstrably lied about a point that matters in the case at hand. The facts that such a witness is asserting might still be true, but they cannot stand without corroboration from another, more reliable witness.
But when corroboration is established, the origins of a conclusion, however tainted, become irrelevant.
As an example, [[Gregor Mendel]] established the genetic theory that remains current today, even though Mendel's experimental technique was badly flawed, and he even stands accused of falsifying key data. But succeeding [[science|scientists]], using accepted methods of verification and statistical assessment, have achieved results consistent with this theory. Thus the theory remains valid even though Mendel's original presentation was fraudulent. Any attempt today to discredit Mendel's theory on account of Mendel's sloppy methods would be an example of a genetic fallacy.<ref name=Genetic>[http://www.fallacyfiles.org/genefall.html Genetic Fallacy] on [http://www.fallacyfiles.org/ The Fallacy Files]</ref>
===Double standard===
The unequal use of a criterion, and its different application in different cases. This is actually a form of [[hypocrisy]].
==Fallacies of Defective or Weak Induction==
==Fallacies of Defective or Weak Induction==
Overgeneralization also is the central problem in trying to conclude something about a population from a non-representative sample, or about a larger group from a non-representative subset of that group.
Overgeneralization also is the central problem in trying to conclude something about a population from a non-representative sample, or about a larger group from a non-representative subset of that group.
====Proving too much====
A form of overgeneralization in which one attempts to use a set of premises to sustain more conclusions than he can reasonably sustain using the argument presented.
==Fallacies of Presumption==
Fallacies of presumption are fallacies in which an unstated or shaky presumption is made.
===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. The typical form of this "argument" is the "conclusion" of a [[non sequitur]].
==Fallacies of Presumption==
===Manufacturing facts from a theory===
: ''Main article: [[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.''
This is yet another form of proof-by-assertion, and is the source of many controversies in modern [[astronomy]], some of them strikingly bitter.
===Circular reasoning===
===Circular reasoning===
Fallacies of ambiguity are fallacies which arise from ambiguity in language used.
Fallacies of ambiguity are fallacies which arise from ambiguity in language used.
==Catalog of Logical Fallacies==
===Equivocation===
===Amphiboli===
===Composition===
===Proving too much===
===Division===
===Double standard===
==Catalog of Logical Fallacies==
===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===
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.
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.
===Tautology===
===Tautology===