Imagine a stream of intellectual enquiry built around the following working hypotheses:
1. There exists a world which is independent of our imagination. That iswe did not make it up; and events in that world are not subject to the control of our wishes.
2. Events in that world have causes which are themselves part of the world.That is, events are neither completely random nor the results of interventions from outside the world.
3. It is possible for normal people to obtain fairly reliable information about events in the world, by careful observation. This does not imply that we will never be mistaken in our observations, only that the observations are not completely unconnected to the world.
4. The purpose of the intellectual enquiry is to use observations to gain an understanding of the world, and in particular of causation. That is, we seek mental models which correctly map the causal processes that occur
in the world.
I should immediately make it clear that I am not asserting the truth of these hypotheses, merely asking for a ‘willing suspension of disbelief’ to permit their discussion. Indeed, I advance them fairly tentatively, conscious that for most of human existence they would have been thought preposterous or impious, and that perhaps the majority of humanity would still find them so.1 The generally agreed explanation has been that events in the world are caused by the intervention of non-worldly beings: gods, demons, spirits, and the like. The only major point of disagreement has been over which beings are responsible.
When the idea that the world might be understood by rational enquiry was first invented2 in Greece, in a remarkably short period about 2,500 years ago, it had to contend not only with conventional Greek mythology but also with other views of what the world is like and what may be understood.