Published online by Cambridge University Press: 12 March 2014
Let L be a first order logic and the infinitary logic (as described in [K, p. 6] over L. Suslin logic
is obtained from
by adjoining new propositional operators
and
. Let f range over elements of ωω and n range over elements of ω. Seq is the set of all finite sequences of elements of ω. If θ: Seq →
is a mapping into formulas of
then
and
are formulas of LA . If
is a structure in which we can interpret
and h is an
-assignment then we extend the notion of satisfaction from
to
by defining
where f ∣ n is the finite sequence consisting of the first n values of f. We assume that has ω symbols for relations, functions, constants, and ω1 variables. θ is
valid if
θ ⊧ [h] for every h and is valid if
-valid for every
. We address ourselves to the problem of finding syntactical rules (or nearly so) which characterize validity
.