 Let us try to understand why the description of the cause should be maximally general. There are three reasons for this. First, this requirement allows us to eliminate potential causal factors that do not contribute to the causal production of the effect. A kernel \(K\) that does mention such a factor—in addition to the “active” causal factors—is less general than a kernel \(K'\) that mentions only the “active” causal factors. Hence, \(K'\) should be preferred over \(K\), other things being equal.