 Reichenbach’s theory is founded on an account of natural laws. He views the logical form of all declarative sentences—modal, counterfactual or otherwise—as specifiable in an extensional first order or typed language. Modality is a property of sentences, not part of their content, and modal sentences therefore involve both a declarative sentence and a meta-language claim about that sentence. As in Carnap’s account, all modality is de dicto. Reichenbach is initially concerned with distinguishing conditionals that, as indicative sentences, are true because of the falsity of their antecedents, from true (or at least assertable) subjunctive conditionals that have false antecedents, or antecedents not known to be true. The former contain uses of propositional connectives (or “operations” in Reichenbach’s terminology) that are inadmissible. Reichenbach’s strategy is to characterize “admissible operations,” that is assertable, subjunctive conditionals, and their truth values, by their deductive relations with indicative “nomological statements.” 