 This condition states that whether e occurs or not depends on whether c occurs or not. Where c and e are events that actually occur, this truth condition can be simplified somewhat. For in this case it follows from the second formal condition on the comparative similarity relation that the counterfactual “If c were to occur e would occur” is automatically true: this formal condition implies that a counterfactual with true antecedent and true consequent is itself true. Consequently, the truth condition for causal dependence becomes: