A → B–if A, then B.
A–A is true.
∴ B–therefore B [is true].
The following is an example of a valid Modus Ponens:
If it is raining, [then] the street will get wet.
It is raining,
Therefore: The street will get wet.
The full name of this form is “Modus ponendo ponens”. Loosely, this could be translated as the “mode of inferring an affirmative [statement] by affirmation [another statement]”.
- Implication elimination
- Affirming the antecedent
- Affirmatio conditionis
Although the MP is intuitively comprehensible for most people, it is not uncommon to make fallacious conclusions on it.
The following table contrasts the modus ponens with its most common errors:
- Modus ponens on Wikipedia