Obviously, our knowledge of the world is quite unlike our hypothetical deity's. We don't know exactly how many particles there are. We don't know their exact properties. We don't know their exact positions.

One important way to distinguish our state of knowledge from the deity's is that for us, there are lots of ways the world might be. If we were shown the deity's memento, even if we had time to examine it, we still could not say with confidence that it is an accurate representation of the world.

This suggests a link between knowledge and possibility. Our state of knowledge is one that is compatible with a number of different ways the world might be. And this is a key difference between our state of knowledge and the state of a being who knows everything. Such a being is in a state that is compatible with only one way the world is. In this chapter, I will explore this link further, and consider how we can represent certain sorts of knowledge in terms of ways the world might be.

A multitude of lists

The deity's memento is a perfect record of the world at a particular time. It consists simply of a table that lists every particle and the physically important properties of each particle: mass, charge, position, velocity, and any others that might feature in the laws.