True or false?

About this video

Can you ask "true or false?" about every sentence? Try it on "Close the door!" and the question sounds strange. Try it on "The door is closed" and it is easy: you look at the door. If it is shut, the sentence is true; if it is open, the sentence is false. A sentence like that, one that says how things are and is either true or false, is called a claim. Logicians also call it a statement.

A claim doesn't have to be true. "Fish can climb trees" is false, but it is still a claim, because it is the kind of sentence that is true or false. Other sentences do different jobs. A question asks, an order tells someone what to do, a greeting says hello and a wish says what we want. None of them is true or false.

Sentences about taste are a special case. "Mango is the best ice cream" can't be checked, because it really tells us about the person who says it. Said honestly, as "I like mango best", it becomes a claim about the speaker. Reasoning is made of claims, which is why finding them is the first step. This video goes with the True or False? and Checking a Claim lessons of Logic Level 1 on Knaph.

Transcript

1. 0:00Close the door! Is that true, or false?
2. 0:04The door is closed. That one, you can check. Look at the door.
3. 0:10Fish can climb trees. False. But it is still a claim.
4. 0:15Questions, orders, greetings and wishes are neither true nor false.
5. 0:21Mango is best? That's taste. Say I like mango best - a claim about you.
6. 0:27A claim is true or false, even before we know which.