Disjunktiver Syllogismus

Lernen

Entweder/Oder-Argumentation: Entweder A oder B, nicht A, daher B.

Disjunctive Syllogism is a rule of inference that eliminates alternatives. Given that 'Either A or B' is true (at least one must hold), and knowing that A is false, we can conclude that B must be true. This is also called 'process of elimination' and is fundamental to decision-making and proof by cases.

P ∨ Q, ¬P ⊢ Q

• Either the package was delivered or it was lost. It was not delivered. Therefore, it was lost.
• Either the answer is 42 or 56. The answer is not 42. Therefore, the answer is 56.
• Either John took the bus or he walked. John did not take the bus. Therefore, John walked.

So erkennen Sie es

• Look for an 'Either...or...' statement (disjunction)
• One of the options is ruled out (negated)
• The conclusion affirms the remaining option

Häufige Fehler

• Assuming 'Either A or B' means exactly one is true (exclusive or). In logic, 'or' typically allows both to be true
• Affirming one disjunct does not eliminate the other: 'Either A or B, A is true' does NOT mean B is false

Übungshinweise

Logische Schlussfolgerung