Logical Fallacies
In order to understand what a fallacy is, one must
understand what an argument is. Very briefly, an argument consists of one or
more premises and one conclusion. A premise is a statement (a sentence that is
either true or false) that is offered in support of the claim being made, which
is the conclusion (which is also a sentence that is either true or false).
There are two main types of arguments: deductive and
inductive. A deductive argument is an argument such that the premises provide
(or appear to provide) complete support for the conclusion. An inductive
argument is an argument such that the premises provide (or appear to provide)
some degree of support (but less than complete support) for the conclusion. If
the premises actually provide the required degree of support for the conclusion,
then the argument is a good one. A good deductive argument is known as a valid
argument and is such that if all its premises are true, then its conclusion must
be true. If all the argument is valid and actually has all true premises, then
it is known as a sound argument. If it is invalid or has one or more false
premises, it will be unsound. A good inductive argument is known as a strong (or
"cogent") inductive argument. It is such that if the premises are true, the
conclusion is likely to be true.
A fallacy is, very generally, an
error in reasoning. This differs from a factual error, which is simply being
wrong about the facts. To be more specific, a fallacy is an "argument" in which
the premises given for the conclusion do not provide the needed degree of
support. A deductive fallacy is a deductive argument that is invalid (it is such
that it could have all true premises and still have a false conclusion). An
inductive fallacy is less formal than a deductive fallacy. They are simply
"arguments" which appear to be inductive arguments, but the premises do not
provided enough support for the conclusion. In such cases, even if the premises
were true, the conclusion would not be more likely to be true.
Inductive
Argument
Premise 1: Most American cats are domestic house cats.
Premise 2: Bill is an American cat.
Conclusion: Bill is domestic house cat.
Factual Error
Columbus
is the capital of the United States.
Deductive
Fallacy
Premise 1: If
Portland
is the capital of Maine, then it
is in Maine.
Premise 2: Portland is in
Maine.
Conclusion: Portland is the capital
of Maine.
(Portland is in
Maine, but Augusta
is the capital. Portland
is the largest city in Maine,
though.)
Inductive
Fallacy
Premise 1: Having just arrived in
Ohio, I saw a white squirrel.
Conclusion: All Ohio Squirrels are white.
(While there are many, many squirrels in Ohio,
the white ones are very rare).
·
Ad Hominem
·
Ad Hominem Tu Quoque
·
Appeal to Authority
·
Appeal to Belief
·
Appeal to Common Practice
·
Appeal to Consequences of a Belief
·
Appeal to Emotion
·
Appeal to Fear
·
Appeal to Flattery
·
Appeal to Novelty
·
Appeal to Pity
·
Appeal to Popularity
·
Appeal to Ridicule
·
Appeal to Spite
·
Appeal to Tradition
·
Bandwagon
·
Begging the Question
·
Biased Sample
·
Burden of Proof
·
Circumstantial Ad Hominem
·
Composition
·
Confusing Cause and Effect
·
Division
·
False Dilemma
·
Gambler's Fallacy
·
Genetic Fallacy
·
Guilt By Association
·
Hasty Generalization
· Ignoring
A Common Cause
·
Middle Ground
·
Misleading Vividness
·
Personal Attack
·
Poisoning the Well
·
Post Hoc
·
Questionable Cause
·
Red Herring
·
Relativist Fallacy
·
Slippery Slope
·
Special Pleading
·
Spotlight
·
Straw Man
·
Two Wrongs Make A Right
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