The new sign

About this video

Arash has studied at the same library for two years, and he knows it closes at 8 in the evening. He has seen it many times. Today, at the door, he sees a new sign: "From 1 March, the library closes at 6 pm." Today is 3 March. What should he believe now?

Of course, that it closes at 6. His old belief had good reasons, but the new evidence is better: it is newer, it comes from the library itself, and it is about exactly this question. Changing a belief when new evidence arrives is called updating it, like updating an app when a new version comes out.

Updating isn't all or nothing. You should change your mind as much as the new evidence says. A sign on the library's own door is strong evidence, so it should change his mind a lot. A friend who says "I think I heard it closes earlier now" is some evidence, so it should change his mind a little, and maybe make him check. A stranger on the bus who says "libraries close at 5" hardly counts at all. And updating isn't a weakness. "I was wrong; it closes at 6" is what a good knower says. The person who never changes their mind isn't strong, they are stuck. This video goes with the Changing Your Mind lesson of Knowledge Level 1 on Knaph.

Transcript

1. 0:00Arash knows the library closes at 8. He's seen it for two years.
2. 0:05Today there's a new sign. From 1 March, closes at 6. Today is 3 March.
3. 0:11So he changes his mind. That's updating a belief.
4. 0:17The library's sign moves you a lot. A friend's guess, a little. A stranger, hardly.
5. 0:23I was wrong, it closes at 6. That's not weakness. That's knowing well.
6. 0:29Change your mind as much as the evidence says.