In logic, Affirming the Consequent is a formal fallacy of reasoning which occurs when one affirms the consequent of a hypothetical statement, without first affirming the antecedent.
Affirming the consequent is also known as converse error and denying the antecedent.
How to calculate
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Begin with a statement of the form “If A, then B”.
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Assume that B is true.
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Conclude that A is true.
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This is a fallacy because it ignores the possibility that B could be true even if A is not true.
Examples
- If a person’s cholesterol level is high, then they are at risk for heart disease. A person has heart disease, therefore their cholesterol level must be high.
- If a person has a high BMI, then they are at risk for health complications. A person has health complications, so their BMI must be high.
- If a person has a high blood pressure, then they are at risk for stroke. A person has had a stroke, so their blood pressure must be high.