Why the world is grey

The observation that the world can be seen as grey, or uncertain, is discussed at a fundamental level. Attention is given first to arguments that suggest that the future should be seen as totally unknown, or black. Reasons are given for dismissing these arguments, and then consideration is given to fundamental causes of uncertainty which prevent the world being white or totally known. The treatment is at a fundamental level that has little bearing on current practical means of dealing with uncertainty, but it is claimed that consideration of fundamentals is often unexpectedly rewarding and therefore worth pursuing.