Logic 101 (#28): Modus Tollens

Modus tollens says that if P implies Q is true and not Q is true as well, then ~P must follow as a result.

For example, suppose

"If I am Miley Cyrus, I am crazy."

and

"I am not crazy."

Then there is no way in hell I am Miley Cyrus.

[ZachBugay]

Definitely appreciated the proof by modus ponens. That helped make the modus tollens a lot clearer as to why it works.

[moniquewrites]

Thank you so much. Translating the word meanings really really helps me to understand the different forms.

[boluwatifeogunnowo]

Thank you for your effort in clarifying this concept

[odinbartsch]

Thank you, best example of modus tollens on youtube

[tylertyler]

How do you know when to use certain logical equivalencies when constructing new ways of saying the same thing or for simplifying the logic, such as you did by converting Modus Tollens to Modus Pollens and using contraposition? Is it just a matter of memorizing all the formulas, rules of inferences, laws, equivalencies, etc. so that it will pop into your head automatically? I'm having to do a lot of research to be able to simplify or convert just one implication. Hope this question makes sense

[anish_r]

that truth table made my life complete

[edtookurbae]

I love how you can tell this came out 10 years ago by the Miley Cyrus being “crazy” reference 😂

[sudevsen]

If it rains then I get wet

Acc to M.T. if I don't get wet then it is not raining

How so? It could be he case that its raining but I am under an umbrella.(which is why I don't get wet)

[PunmasterSTP]

Q: What does a logical eagle use to catch its prey?








A: Modus talens.

😎

[joeyt]

why is this different from reductio ad absurdum

[naomiruwainegutierrezparri]

can you make a video about how to complete the truth table?

[rahaftamimi]

I think this guy hates Miley Cyrus, However he is perfect 🤣