What is a*sequential-state*problem? This is a question that is most directly answered by giving some specific examples. One*can*, I should admit, formulate a theoretical, mathematical definition, but examples are both more illuminating and, even more importantly, I think, more*fun*. My first example will drive home the point made by the opening quotation, that the concept of a physical system changing state with time predates Shannon and Boole by centuries. In fact, you’ll see how the state concept predates*Newton*by even more centuries. This first example of the state concept comes from a late ninth century