**Structure and Parts** Variables (the only type of nodes allowed) Relationships one type only--affects, influence, causes Two Directions possible for each relationship (same direction--supporting or opposite direction--opposing) Delay Feedback--two types of feedback: same (reinforcing, growth) and opposite (balancing, limits) **Three Change Dynamics** Exponential (growth and collapse) Control (keeping variable level within limits) Leverage (small effort big effect) **One Bounding Concept** Boundary/Environment/Inside-Outside **Two Questions** Interesting? / Important? What else?