IDEA FOUND // IDEA 114
Denying the Antecedent
“Closing one route does not prove the destination is unreachable.”
01 / PLAINLY
What it means, plainly
Denying the antecedent assumes that because A can lead to B, the absence of A rules out B. The step fails when B has another route.
02 / CONTEXT
A little more
The invalid form is: if A, then B; not A; therefore not B. A can be sufficient for B without being the only way to obtain B.
03 / WHY IT MATTERS
Why it matters
It stops you from ruling out outcomes, solutions, or explanations merely because one particular path was missing.
04 / EXAMPLE
A familiar example
If I take the train, I reach downtown. I did not take the train. I might still have arrived by bicycle.
05 / LIMIT
What it does not mean
Confusing a sufficient condition with a necessary one erases genuine alternatives.
06 / NOTICE
Notice it in your day
Name a goal with two different routes to it. Show why losing one route does not make the goal impossible.
FINAL NOTE
The idea worth keeping
Before denying B, ask whether routes other than A were available.
QUESTIONS / 02
Questions people still have
What does this fallacy confuse?
It confuses a sufficient condition with a necessary one.
Before denying B because A did not occur, what should you check?
Whether another cause or route could still produce B.