more from E Reck / M Price

### Single Idea 10175

#### [catalogued under 5. Theory of Logic / G. Quantification / 5. Second-Order Quantification]

Full Idea

In second-order logic there are three kinds of variables, for objects, for functions, and for predicates or sets.

Gist of Idea

Three types of variable in second-order logic, for objects, functions, and predicates/sets

Source

E Reck / M Price (Structures and Structuralism in Phil of Maths [2000], §5)

A Reaction

It is interesting that a predicate seems to be the same as a set, which begs rather a lot of questions. For those who dislike second-order logic, there seems nothing instrinsically wicked in having variables ranging over innumerable multi-order types.