  Of course, we want a planning agent to be able to infer in such a case that a performance of turn-on will result in a situation in which the ignition is on, the battery isn’t dead, and the engine is running. But contraposition of laws makes it difficult to devise a principled solution. Informally, this difficulty is this: we can conclude by contraposing our only static law that if the ignition is on and the engine isn’t running, then the battery is dead. This law not only is true in our scenario, but would be used to explain a failed attempt to start the car. But if we allow it to be used for prediction, then it is hard to see how to rule out an outcome of turn-on in which the ignition is on, the battery is dead, and the engine isn’t running. The battery is dead in this outcome because of causal inertia. The engine isn’t running because of the contraposed causal law.