''(See XpSimplicityRules for what seems to be the non-deprecated version)'' From ExtremeProgrammingExplained (p109): 1. The system (code plus tests) clearly communicates everything that needs to be communicated at the current instant in its development. This means that it runs every existing test, and that the source code clearly reveals the intention behind it to anyone who reads it. 1. The system contains no duplicate code, unless that would violate (1). 1. The system contains the minimum number of classes possible without violating (1) or (2). 1. The system contains the minimum number of methods possible, consistent with (1) (2) and (3). The problem with this wording is that (1) is overloaded (thus de-emphasized) and (3) and (4) are underloaded (thus emphasized). This leads to the confusion as found on "MinimumNumberOfClassesAndMethods".