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constructive dilemma

Two conditionals plus "one condition or the other" give "one result or the other."

Constructive dilemma is the valid form: if P, then Q; if R, then S; P or R; therefore Q or S. It works like modus ponens applied to two conditionals at once.

Examples

  • "If I take the bus, I'm late. If I drive, I pay for parking. I'll take the bus or drive. So I'm late or I pay for parking."

See also

destructive dilemma modus ponens
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