 Cases of preemption show us that causes need not be necessary for their effects. The effect e did not depend upon its cause c. Had c been absent, e would still have happened, due to the backup b. They moreover suggest that there is something important about the process whereby causes and effects are connected. Both c and the backup b were sufficient for e to happen. What seems to make the difference between them is that there is the right kind of connecting process leading from c to e, and there is not the right kind of connecting process leading from b to e. For this reason, while counterfactual, probabilistic, agential, and regularity theories often stumble on cases of preemption, they are more easily treated by process theories.