Logic / Unit 4 Logic 151 short lesson, about 20 seconds
Modus Tollens
Captions available
The idea
If p then q; not-q; therefore not-p. Always valid.
In practice
If the fuse blew, the lights are out. The lights are on. The fuse didn't blow.
Where people slip
MT runs the conditional backward through the negations — the only legal reverse gear.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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