From the Publisher's Website:
Sin/Zen is an experimental game system, with a mechanic based on the Seven Deadly Sins and Zen philosophical concepts. Characters are Entities of power in any of a number of possible game worlds. An Example game world is touched on, Γνοθη Σεαυτον (Gnothi Seafton), based on the Ancient Greek Mythos.
Characters are motivated by their Passions, based on the Seven Deadly Sins, and rated from 0 to 6. Action resolution involves rolling two (twelve-sided) dice and picking the lower. The action fails is this number is greater than a target number that is the sum of the "Active Motivation" of the acting character and the "Passive Vulnerability" of the opposing character.