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.