Chapter 3: Graded Causation and Normality
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Chapter 3 Graded Causation and Normality Perhaps the feelings that we experience when we are in love represent a normal state. Anton Chekhov In a number of the examples presented in Chapter 2, the HP deﬁnition gave counterintuitive ascriptions of causality. I suggested then that taking normality into account would solve these problems. In this chapter, I ﬁll in the details of this suggestion and show that taking normality into account solves these and many other problems, in what seems to me a natural way. Although I apply ideas of normality to the HP deﬁnition, these ideas should apply equally well to a number of other approaches to deﬁning causality. This approach is based on the observation that norms can affect counterfactual reasoning. To repeat the Kahneman and Miller quote given in Chapter 1, “[in determining causality], an event is more likely to be undone by altering exceptional than routine aspects of the causal chain that led to it”. In the next section, I give a short discussion of issues of defaults, typicality , and normality. I then show how the HP deﬁnition can be extended to take normality into account. The chapter concludes by showing how doing this deals with the problematic examples from Chapter 2 as well as other concerns. 3.1 Defaults, Typicality, and Normality The extended account of actual causation incorporates the concepts of defaults, typicality, and normality. These are related, although somewhat different notions: A default is an assumption about what happens, or what is the case, when no additional information is given. For example, we might have as a default assumption that birds ﬂy. If we are told that Tweety is a bird and given no further information about Tweety, then it is natural to infer that Tweety ﬂies. Such inferences are defeasible: they can be overridden by further information. If we are additionally told that Tweety is a penguin, we retract our conclusion that Tweety ﬂies. 77 78 Chapter 3. Graded Causation and Normality To say that birds typically ﬂy is to say not merely that ﬂight is statistically prevalent among birds, but also that ﬂight is characteristic of the type “bird”. Although not all birds ﬂy, ﬂying is something that we do characteristically associate with birds. The word normal is interestingly ambiguous. It seems to have both a descriptive and a prescriptive dimension. To say that something is normal in the descriptive sense is to say that it is the statistical mode or mean (or close to it). However, we often use the shorter form norm in a more prescriptive sense. To conform with a norm is to follow a prescriptive rule. Prescriptive norms can take many forms. Some norms are moral: to violate them would be morally wrong. For example, many people believe that there are situations in which it would be wrong to lie, even if there are no laws or explicit rules forbidding this behavior. Laws are another kind of norm, adopted for the regulation of societies. Policies that are adopted by institutions can also be norms. For instance, a company may have a policy that employees are not allowed to be absent from work unless they have a note from their doctor. There can also be norms of proper functioning in machines or organisms. There are speciﬁc ways that human hearts and car engines are supposed to work, where “supposed” here has not merely an epistemic force, but a kind of normative force. Of course, a car engine that does not work properly is not guilty of a moral wrong, but there is nonetheless a sense in which it fails to live up to a certain kind of standard. Although this might seem like a heterogeneous mix of concepts, they are intertwined in a number of ways. For example, default inferences are successful to the extent that the default is normal in the statistical sense. Adopting the default assumption that a bird can ﬂy facilitates successful inferences in part because most birds are able to ﬂy. Similarly, we classify objects into types in part to group objects into classes, most of whose members share certain features. Thus, the type “bird” is useful partly because there is a suite of characteristics shared by most birds, including the ability to ﬂy. The relationship between the statistical and prescriptive senses of “normal” is more subtle. It is, of course, quite possible for a majority of individuals to act in violation of a given moral or legal norm...