Don't patternize me, dude











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Recognizing and Using Common Logical Forms

The table below shows the most general presentation for commonly occurring forms of valid arguments and fallacies.

It is important to understand that the occurrence of a common form depends upon the relationship between its terms, not upon the names given to those terms.

For example, both of these arguments are Direct Reasoning:
pq
p
q

~qp
~q
p

It is also important to understand that it doesn't matter which premise is listed first or which premise is listed second.

For example, both of these arguments are Direct Reasoning:
p
pq
q

~q
~qp
p

VALID FORMSINVALID FORMS
Direct Reasoning
AB
A
B

One premise is an if...then statement, the other premise affirms the antecedent, and the conclusion affirms the consequent.
Fallacy of the Converse
AB
B
A

One premise is an if...then statement, the other premise affirms the consequent, and the conclusion affirms the antecedent.
Contrapositive Reasoning
AB
~B
~A

One premise is an if...then statement, the other premise denies the consequent, and the conclusion denies the antecedent.
Fallacy of the Inverse
AB
~A
~B

One premise is an if...then statement, the other premise denies the antecedent, and the conclusion denies the consequent.
Transitive Reasoning
AB
BC
AC

One premise is an if...then statement, another premise is an if...then statement whose antecedent matches the consequent of the other premise, and the conclusion results from this chain of reasoning.
False Chains
AB
AC
BC


AB
CB
AC

An incorrect attempt at Transitive Reasoning, in which two if...then premises agree in the antecedent, or agree in the consequent.
Disjunctive Syllogisms
AB
~B
A


AB
~A
B

One premise is an "or" statement, the other premise denies part of the "or" statement, and the conclusion affirms the other part.
Disjunctive Fallacies
AB
B
~A


AB
A
~B

One premise is an "or" statement, the other premise affirms part of the "or" statement, and the conclusion may affirm or deny the other part.

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