No x′ are m;
No m′ are y.


∴ No x′ are y.

i.e. No one, but John, knows what the letter is about.

3. Those who are not old like walking;
You and I are young.

Univ. is “persons”; m = old; x = persons who like walking; y = you and I.


All m′ are x;
All y are m′.


∴ All y are x.

i.e. You and I like walking.

4. Your course is always honest;
Your course is always the best policy.

Univ. is “courses”; m = your; x = honest; y = courses which are the best policy.


All m are x;
All m are y.


∴ Some x are y.

i.e. Honesty is sometimes the best policy.