 We have struck through the original equation for Flame to show that it is no longer operative. The result is a new world with a modified causal structure, with Gas level = 3, Flame = 1, and Meat cooked = 1. Since the equation connecting Flame to its causes is removed, any changes introduced by setting Flame to 1 will only propagate forward through the model to the descendants of Flame. The intervention changes the values of Flame and Meat cooked, but it does not affect the values of the other variables. We can represent interventions on multiple variables in the same way, replacing the equations for all of the variables intervened on.