The logic of Watson is dominated by three themes. It is *algebraic* (equational). An important role is played by *definition by cases*. Its higher order logic uses *stratified
abstraction*. In this section, we will use notation closer to
conventional mathematical notation than to Watson's internal language,
which will be introduced in the next section.

- Algebraic logic
- Definition by cases
- Stratified abstraction
- The relationship between stratified -calculus and usual type theories
- Strongly cantorian domains