Logic and kids

Logic

 

Once upon a time (long ago!) I was talking to my grandson Alex’s  grade 4 class about logic. One thing I talked about with them was different kinds of logical statements:

A: All S are P.       – [universal affirmative]
I: Some S are P.  – [particular affirmative]
E: No S are P.      – [universal negative]
O: Some S are not P.   – [particular negative]

I went over that stuff a bit and then asked them for examples. They were eager to provide them!

“Some teachers are not good” and “All recesses are great” and so on…
Then I asked a next level question about universal affirmatives: OK, all apples are fruits, but are all fruits apples? NO!

Can anyone give me an example where you can switch terms in an A statement and it will still be true?

“All teachers are women”?

No, if we switch we get “all women are teachers” – is that true.

“No!” they said. And offered counter-examples.

After a minute or two a kid in the back raised her hand.

“All dogs are dogs”?

She recently graduated from VIU with a degree in philosophy.