Of God and His Creatures

St Thomas does not view causation dynamically, but statically. I mean, a cause to him is not a being which by its changing propagates a change to some other being, -- as when one ninepin falling knocks over another ninepin, and so on to the end of the row: this he calls, not causatio, but motio, and such are the causes of causation usually considered by physicists, but causation in St Thomas points to dependence of being, and a cause is a being on which another being, its effect, is more or less permanently dependent for its existence: that is why he makes quite as much of material and formal and final as of efficient causation.

Of God and His Creatures: 3.49