Logicians are doing semantics when they are setting up conditions on what the truth values of the several propositions under consideration may be. Setting up these truth conditions for propositions is by far the most important aim of logical semantics and in this respect logical semantics differs considerably from what linguists usually call ‘semantics’. Though the concept of truth, and its use in logical semantics, conjures up several important philosophical and ontological issues, the distinction between (logical) syntax and (logical) semantics is, in general, quite clear. In the syntax we have formation rules, proofs, derivations that can all be defined in terms of the (formal) properties of the expressions under consideration, whilst in the semantics we have notions like truth, denotation and reference, properties which expressions may have relative to one model but not to another. Although this distinction is itself ancient and goes back to the distinction between form and content, it will be often difficult, especially when the kind of semantics outlined above is applied to natural language, to draw a sharp distinction between the purely syntactic and purely semantic sides of the system, as it is evident that several properties may be reflected both in the syntax and in the semantics. Techniques from formal semantics have, however, have proven to be very useful in the analysis of natural languages (e.g. in Montague grammar and intensional logic).