Why is the argument about Othello being male an example of denying the antecedent?

The argument "If Othello is a bachelor, then he is male; Othello is not a bachelor; therefore, Othello is not male" is a classic example of the formal fallacy known as denying the antecedent.1

This reasoning is invalid because it follows the flawed structure: "If A, then B; not-A; therefore, not-B". In this specific case:1
* A (the antecedent): Othello is a bachelor.
* B (the consequent): Othello is male.

The error lies in assuming that because the condition "being a bachelor" is false, the result "being male" must also be false. However, the original premise only establishes that being a bachelor is a sufficient condition for being male; it does not state that it is the only way to be male. Othello can be male for other reasons (such as being a husband), meaning the negation of the antecedent does not guarantee the negation of the consequent.12

Are you interested in learning about other types of formal fallacies, such as affirming the consequent?