Hard Tweets Explained: Contraposition


Contraposition is a logic term that I’m guessing most people don’t know. Here is a simple example.

Me: Did you brush your teeth?

7: Yes!

Me: (checks toothbrush, it is dry)

7: Oh! You mean today?

We start with a conditional implication that if she brushed her teeth, then the toothbrush would be wet.

Brushed —implies—> Wet

We don’t know whether she brushed her teeth, but we do know that the toothbrush is not wet. The logical principle of contraposition (also called modus ponens) says that if you are certain that P->Q, then you can be certain that (not Q)->(not P). If brushed implies wet, then not-wet implies not-brushed.

Note that wet does not imply brushed. Now that 7 is 8…

View original post 191 more words

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this:
search previous next tag category expand menu location phone mail time cart zoom edit close