DISCUSSION
COMMENTS ON DR. VETTER'S PAPER
'DEONTIC LOGIC WITHOUT DEONTIC OPERATORS'* 1. Vetter's paper contains interesting contributions to a still rather controversial subject: deontic logic. He proposes to substitute systems of deontic logic containing the operators 'permitted' and 'obligatory' by a system containing the deontic predicate 'admissible' (A) instead. All predicates of his system are one-place and their variable's' ranges over state descriptions in the Carnapian sense.
He defines the operators 'obligatory' and 'permitted' by means of his system:
(his (10)) !p-(s) (As=Ps) which means: p is obligatory, iff every admissible state description is in the range of p, where "the range ofp is the set of state descriptions whose disjunction is equivalent to p.,U
(his (11)) w -(Es) (as &es)
which means; p is permitted, iff there is an admissible state description in the range ofp.
The definitions permit to translate the axioms von Wright uses 2 into Vetter's system, which, insofar at least, provides a model of von Wright's system.
- What now are the merits of Vetter's new approach? One advantage he claims is "that it is not necessary to devise any special rules.., at all in our system: everything is settled automatically by the inference rules of the Predicate Calculus. ''3 This is a very bold idea, if we take into consideration that e.g. his only syntactical means to introduce the operator '!' is a conditionalization. The prescriptive (or perhaps deontic) character of the predicate A cannot have any influence on syntax, which a descriptively interpreted predicate in the same place would not have, because there are no special syntactical rules for prescriptive predicates.