Is it raining in Z-land? 2015. 20 minutes.
Z-land is a hypothetical place described in a paper by the American philosopher John Perry. It is identical in almost every respect to a small town in the North of England called Rotherham. The main difference between Z-land and Rotherham is that one exists and the other does not. Z-land, like Rotherham, has a number of inhabitants all of whom are unaware, as they go about their daily lives, that they are nothing more than extras in a philosophical thought-experiment.
Consider a small isolated group, living in a place we call Z- land. Z-landers do not travel to or communicate with residents of other places, and they have no name for Z-land. When a Z- lander sees rain, he will say to others not in a position to look outdoors, 'It is raining'. His listeners then act appropriately to there being rain in Z-land: they close the windows in Z-land, cancel plans for Z-land picnics, and grab umbrellas before going into the Z-land out-of-doors. They have no other use for 'It is raining'. They do not call their sons in far-off places, or listen to the weather news, or read newspapers with national weather reports. Thought without Representation, John Perry (1986)
The experiences and thoughts about objects that we have over a period of time are similar to the experiences and thoughts the Z-landers would have while moving from one place to another. They would perceive one place, then another, but from their point of view nothing would seem different except, for example, whether it was raining. They would entertain a constant propositional function that would yield a series of different propositions. In a similar way we experience one temporal part of an object at one time and another temporal part at another time, but from our point of view it always seems to be the same entity. And, of course, the same principle applies to thoughts about oneself. Each temporal part of an object is experienced by a corresponding temporal part of the subject, but from the subjectís point of view the experiences all seem to belong to a single subject that wholly exists at each moment in time. Temporal Metaphysics in Z-land, Simon Prosser (2006)