A Predicate Calculus

1.1 The relation α 1,.., α n ├α, or ├ α n α. As we have already explained in Chap. I, § 5, we want to lay the rules of down a calculus with the help of which we can obtain al-gorithmically all the consequences of arbitrary sets of expressions. Various different calculi of this sort are known today; every such calculus is called a predicate calculus or, more precisely, a first-order predicate calculus. (For predicate caluculus of higher order cf. Chap. VI, § 1.) In the next section, we shall give a particularly simple calculus of this sort. For the sake of simplicity, we shall call this calculus the predicate calculus (instead of a, predicate calculus).