The reason for the tremendous representation inefficiency of propositional logic is that it does not contain the concept of an object.  When we think about the world, we always think about objects --- people, cars, cities, even talks --- are viewed as separate entities.  Each of these has its own properties, or attributes.  And, they are all linked to each other via a complex network of interactions.  A yet more transparent representation is relational logic.  In this case, the possible worlds specify a set of objects, their properties, and the relations between them.  By making objects explicit, we can now generalize over them, specifying universal patterns that apply to all objects.  This allows us to state many things at once, and provide a much more compact representation.  In particular, the rules of chess now require only about 100 axioms.