--- John D. Sterman(2002) “All models are wrong: reflections on becoming a systems scientist: The Jay Wright Forrester Prize Lecture.” System Dynamics Review Vol. 18, No. 4, (Winter 2002): 501–531
Full quote: There are no side effects—only effects. Those we thought of in advance, the ones we like, we call the main, or intended, effects, and take credit for them. The ones we didn’t anticipate, the ones that came around and bit us in the rear—those are the ‘‘side effects’’.