Chapter 6, Tutorial 2
Categorical Logic and Venn diagrams
In 6.1 we introduced the logic of quantities. The new symbols here are the existential ('%') and universal ('^') quantifiers. Still, we restricted all discussion to a single subject matter: our "universe of discourse" included a single subject, for example Cats. We need to loosen that restriction and gradually work up to the full logic of quantities. We begin with categorical logic later in this tutorial. But there are important lessons to learn from the restricted case.
The last exercise in 6.1 is very important. If you've not yet done this one, this would be the time: 6.1d.
This exercise deals
with cats alone: