1. A lattice-theoretical fixpoint theorem. In this section we formulate and prove an elementary fixpoint theorem which holds in arbitrary complete lattices. In the following sections we give various… Expand

By a decision method for a class K of sentence (or other expressions) is meant a method by means of which, given any sentence θ, one can always decide in a finite number of steps whether θ is in K;… Expand

The logical theory which is called the calculus of (binary) relations , and which will constitute the subject of this paper, has had a strange and rather capricious line of historical development.Expand

The formalism $\mathcal L$of predicate logic The formalism $\mathcal L^+$, a definitional extension of $\mathcal L$ The formalism $\mathcal L^+$ without variables and the problem of its equipollence… Expand