Affirming a disjunct

Affirming a disjunct is a form of logical fallacy where an alternative possibility is rejected because the first is accepted, even if both are accurate. The problem with this fallacy is typically an underlying misunderstanding that establishes false mutual exclusivity and/or a false dichotomy.

Formal Construction

 * A or B
 * A
 * Therefore, it's not B

Examples

 * Evolution
 * 1) Evolution is either a theory or a fact
 * 2) Evolution is a theory
 * 3) Thus, Evolution is not a fact


 * Choice of Religion
 * 1) Either God is the Muslim god or he is the Christian god.
 * 2) God is the Christian god
 * 3) Thus, God is not the Muslim god


 * Choice of God or Evolution
 * 1) Either God created animals or they evolved over time
 * 2) God created animals
 * 3) Thus, Evolution is false

Ways to Avoid Affirming a Disjunct
Make sure that the two initial possibilities are in fact mutually exclusive. Try to think of ways that both - or neither - could be true, and thus ways that the argument could be invalid.