1. A method executed on a computing device for determining document classification probabilistically through classification rule analysis, the method comprising: identifying patterns and evidences within content of representative documents; constructing a classification rule based on an entity determined according to an analysis of the patterns and an affinity determined according to an analysis of the evidences; processing the content with the classification rule to: determine an entity count and an entity confidence level for the entity; determine an affinity presence and an affinity confidence level for the affinity; aggregate the entity count, the entity confidence level, the affinity presence, and the affinity confidence level to returned results; comparing the returned results to expected results to evaluate the classification rule against acceptance requirements; and if the classification rule meets the acceptance requirements, identifying confidence levels for the patterns and the evidences; else editing the classification rule.