Nature's Capacities and Their Measurement by Nancy Cartwright

Author:Nancy Cartwright [Cartwright, Nancy]
Language: eng
Format: epub
ISBN: 0198235070

34 E. Eells, 'Probabilistic Causal Levels', in Skyrms and Harper, op. cit., 79-97.

35 Ibid.

36 Ibid.

end p.137

not use CC*. For Eells, there is neither any singular causal input nor any singular causal output.

An immediate problem for Eells's proposal is that the causal laws it endorses seem to be wrong. Consider again the population of women who have not become pregnant by time t 2. On the proposal that lines up correlations and causes, only one generic relation between pills and thrombosis is possible, depending on whether the pills increase the probability of thrombosis or decrease it. For this case that is the law that says: 'In this population, pills cause thrombosis.' That much I agree with. But it is equally a consequence of the proposal that the law 'In this population, pills prevent thrombosis' is false; and that is surely a mistake. For as the case has been constructed, in this population most of the women will have been saved from thrombosis by the pills' action in preventing their pregnancy. What is true in this population, as in the population at large, is that pills both cause and prevent thrombosis.

Eells in fact substantially agrees with this view in his most recent work. His forthcoming book37provides a rich account of these singular processes and how they can be treated using single-case probabilities. The account is similar in many ways to that suggested in Principle*. Eells now wants to consider populations which are defined by what singular counterfactuals are true in them, about what would happen to an individual if the cause were to occur and what would happen if it were not to. The cause 'interacts' with the different sub-populations which are homogeneous with respect to the relevant counterfactuals. His notion of interaction seems to be the usual statistical one described on page 164; basically, the cause has different probabilistic consequences in one group than in another. It looks, then, as if we are converging on similar views.

That is Eells himself. I want to return to the earlier work, for it represents a substantial and well-argued point of view that may still seem tempting, and I want to be clear about what kinds of problems it runs into. In the earlier work of Eells all that is relevant at the generic level are the total numbers—does the probability of thrombosis go up or down, or does it stay the same? But to concentrate on the net outcome is to miss the fine structure. I do not mean by fine structure just that Eells's account leaves out the ornateness of detail that would come with the recounting of individual histories; but

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