One stone thrown into a pool of water makes a “simple” and “intelligible” pattern– concentric circles going out from the point of entry of the stone. Two stones produce a more complex but still easily graspable pattern as the circles intersect. Three stones produce a disturbance of the water so complex that if you didn’t know in advance how it was produced, it would take sophisticated analytic techniques to figure it out. The appearance of complexity does not rule out causal simplicity.