Modus ponens is a valid "If A happens, B happens in consequence. A happens. Then B also happens". A "modus ponens fail", also called "affirm the consequence" is the invalid "If A happens, B happens in consequence. B is observed. Then A happened".
Valid: if someone is hit by a train, he dies. Someone was hit by a train, then he is dead.
Invalid: if someone is hit by a train, he dies. Someone is found death, thus he must have been hit by a train.
Modus ponens is a valid "If A happens, B happens in consequence. A happens. Then B also happens". A "modus ponens fail", also called "affirm the consequence" is the invalid "If A happens, B happens in consequence. B is observed. Then A happened".
Valid: if someone is hit by a train, he dies. Someone was hit by a train, then he is dead.
Invalid: if someone is hit by a train, he dies. Someone is found death, thus he must have been hit by a train.
I need this for most HN comments myself. Glad I joined this site to learn where I fall on the bell curve.
non sequitur
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