Affirming the consequent

From RationalWiki

Affirming the consequent is a logical fallacy often used in the context of trying to establish guilt by association. It is named after the consequent in a conditional statement (Q in "if P, then Q").

Contents 1 Forms of the argument 1.1 Propositional logic 1.2 First-order logic 2 Examples of the argument 2.1 Propositional form 2.2 First-order form 3 See also

[edit] Forms of the argument

[edit] Propositional logic

• If P, then Q.
• Q.
• Therefore, P.

In formal terms, the fallacious argument is stated as .

[edit] First-order logic

• If P is true of x, then Q is true of x.
• Q is true of x.
• Therefore, P is true of x.

In formal terms, the fallacious argument is stated as .

[edit] Examples of the argument

[edit] Propositional form

• If it is sunny today, then I will go swimming.
• I will go swimming.
• Therefore, it is sunny today.

[edit] First-order form

• Fascists support a strong military.
• John Q. Warhawk supports a strong military.
• Therefore, John Q. Warhawk is a fascist.

[edit] See also

• Post hoc, ergo propter hoc
• Causalation
• Correlation does not equal causation