ABSTRACT
There are many events that we cannot observe directly, but nevertheless understand because of our observations and assumptions about patterns of human behaviour. We regularly assume that people who have routinely done particular things in the past, such as delivering newspapers or stealing cars, will continue to do so, even if we know little about them, their methods or their motivations. Also, we assume that certain sets of events, such as the regular appearance of a local newspaper in our mailbox or the recurrent sounding of a car burglar alarm, are the result of the acts of a particular individual, even though we may have no idea who that person is or precisely how or why the events are occurring.
