Its degree of simplicity and its scope determine the intrinsic probability of a theory, its probability independent of its relation to any evidence. The simpler a theory, the more probable it is. The simplicity of a theory, in my view, is a matter of it postulating few (logically independent) entities, few properties of entities, few kinds of entities, few kinds of properties, properties more readily observable, few separate laws with few terms relating few variables, the simplest formulation of each law being mathematically simple. … A theory is simpler and so has greater prior probability to the extent to which these criteria are satisfied.