  Lewis begins by studying signaling problems. A communicator has privileged information differentiating among states \(s_{1},\ldots, s_{m}\). Audience members can choose among responses \(F(s_{1}), \ldots, F(s_{m})\). Everyone prefers that audience members do \(F(s_{i})\) if \(s_{i}\) obtains. There is a set of signals \(x_{1},\ldots,x_{n}\), \(m \le n\), that the communicator can pass to the audience. In Lewis’s example, the sexton knows whether the redcoats are staying home, coming by land, or coming by sea. By placing either zero, one, or two lanterns in the belfry, he signals Paul Revere whether to go home, warn people that redcoats are coming by land, or warn people that the redcoats are coming by sea. A signaling problem is a coordination problem, because communicator and audience must coordinate so that the communicator’s signal elicits the mutually desired action. Building on Lewis’s discussion, Skyrms (2010) offers an intensive analysis of signaling problems, with applications to diverse biological cases studies ranging from bacteria to apes.