ABSTRACT
Whatever knowledge people possess is either knowledge of particular facts or scientific knowledge. The details of history and geography lie outside science in a sense; that is to say, they are presupposed by science, and form the basis upon which it is a super-structure. Most people would say that the sun does come within our direct experience in a sense in which Napoleon does not, but in thinking this they would be mistaken. The sun is removed from people in space as Napoleon is removed from them in time. It is characteristic of the advance of science that less and less is found to be datum, and more and more is found to be inference. Physics has been compelled by its own necessities to take account of some of these unwarrantable prejudices. The plain man thinks that matter is solid, but the physicist thinks that it is a wave of probability undulating in nothingness.
