INUS Analysis of Causation
Mackie’s Plan: Use the INUS analysis to explain singular and general causal statements: a cause of an event is at least an INUS condition of it. The notion of INUX condition is explained in terms of necessary and sufficient conditions, and these are analyzed in terms of counterfactuals which are analyzed on the nomic-inferential model. It is here that laws enter into the story; Mackie regards himself as supplying a form of a regularity theory of causation.
— Definitions —
I. A condition C is a cause of an effect E if C is an Insufficient but Necessary part of a condition C+ that is itself Unnecessary but Sufficient for E in the relevant context. (34)
II. A is an INUS condition of a result P iff, for some X and for some Y, (AX or Y) is a necessary and sufficient condition of P, but A is not a sufficient condition of P and X is not a sufficient condition of P. (35)
— Gloss 1: AX is what Mackie (following Marc-Wogau) calls a “minimally sufficient condition” for P in that it contains no redundant conditions, and each part is necessary for the production of P on that occasion.
— Gloss 2: It is crucial to Mackie’s analysis that there be other MSCs for P; if not, then AX is not unnecessary and so A is not an INUS condition. Thus, Y must be non-empty. In many cases, though, Y will be a lengthy disjunction of additional MSCs.
III. A is at least an INUS condition for P iff there is a necessary and sufficient condition for P that is of one of these forms: (AX or Y), (A or Y), AX, or A. (36)
IV. When one makes the claim, ‘A caused P’, one is often (implicitly) claiming:
A. A is at least an INUS condition for P in the field F. (See §3 in Mackie)
B. A was present on the occasion in question.
C. The factors represented by the ‘X’, if any, in the formula for the necessary and sufficient condition were present on the occasion in question.
D. Every disjunct in ‘Y’ which does not contain ‘A’ as a conjunct was absent on the occasion in question.
— Gloss 1: The field F is a causal field. A causal field is a field in which you are looking for the cause of an event. It represents the region that is to be divided by the cause. For example, if you ask, “What causes influenza?”, you may mean in all organisms susceptible to types of the disease, or you may mean to restrict your focus to human beings alone. These represent two different causal fields.
— Gloss 2: The elements in the MSC might be identified as “triggering causes” and “structuring causes”, or they might be distinguished in other ways.
E. To say that Z is a necessary and sufficient condition for P in F is equivalent to ‘All FP are Z and all FZ are P’, where ‘F’ refers to the causal field.
— Gloss: Mackie understands the necessity condition as a counterfactual conditional, and the sufficiency condition as a “factual” conditional. Further, he recommends that we interpret these as condensed or incomplete arguments: given the conjunction of additional “universal propositions” and “true statements of the features of F” with the stated premise, we get the stated conclusion.
— Problems —
III. The analysis in IV is an analysis of singular causal statements, where ‘A’ and ‘P’ are meant to refer to specific events. As Kim points out (69-70), it is very difficult to make sense out of this analysis in connection with singular causal statements, since (B) seems redundant in that case and it is very difficult to make out how the conditions on INUS are satisfied. Kim suggests we restrict this to general causal statements, pace Mackie. This seems correct.
IV. What of causal overdetermination? For example, say a person dies when two bullets pierce his heart at the same time. Or two radios, tuned to the same station and both turned on, begin playing the same music when the station begins its broadcasting day. There are several types of overdetermination (e.g., independent, simultaneous, and linked overdetermination), all of which seem to threaten the INUS analysis, assuming that this analysis is supposed to be general. (See Scriven)
V. Kim raises numerous difficulties for the account, arguing that Mackie uses logical operations in a way that might be fine in propositional logic, but doesn’t play at all well when you deal with events as opposed to propositions. His main charge: “It seems to me that the difficulties under discussion are symptomatic of an underlying confusion of events with their descriptions.” As a result, the linguistic and ontological framework underpinning Mackie’s analysis is a mess. Kim attempts to rectify the situation, though, and offers an alternative to (IV) above on p. 73.