Lecture 6


Problems With The Causal Theory Of Explanation

Last time we finished our exploration of the content of causal theories of explanation, including the kinds of caveats that have to be added to make the theory workable. Today, we will examine whether the causal approach as a whole is plausible, and examine an alternative view, namely van Fraassen's pragmatic theory of explanation. (Note Kourany's use of the term "erotetic.") As I stated at the end of the period last time, there are two basic challenges that can be given to the causal view, namely that sometimes non-causal generalizations can explain, and that laws can be explained by other laws (a relationship that does not seem to be causal, since laws don't cause other laws, since neither is an event).

(1) Non-causal generalizations - Suppose that someone was ignorant of the various gas laws, or once learned the laws and has now forgotten them.

General Law: PV = nRT

Boyle's Law: At constant temperature, pressure is inversely proportional to volume, i.e., PV = constant.

Charles' Law: At constant pressure, volume is directly proportional to temperature, i.e., V/T = constant.

Pressure Law: At constant volume, pressure is directly proportional to temperature, i.e., P/T = constant.

They wonder why it is that a certain container containing gas expands when heated. You could then give various answers, such as that the pressure was constant, and then cite Charles's law to finish the explanation. Alternately, you might say that there was a more complex relationship, where the pressure increased along with the temperature, but that the increase in pressure was not enough to compensate for the increase in temperature to that the volume had to rise too, according to the general gas law. Q: Is this an explanation? We have to distinguish whether it's the "ultimate" or "fundamental" explanation of the phenomenon in question or whether it's an explanation of the phenomenon.

Example from statics: an awkwardly posed body is held in place by a transparent rod. Why is it suspended in that odd way? Well, there's a rod here, and that compensates for the force of gravity.

Example from Lewis, the collapsing star: Why did it stop? Well, there is no causal story that we can tell, other than by giving "negative" information: there was no state for it to get into if it collapsed further, because of Pauli Exclusion Principle. (Here identical fermions cannot have the same quantum numbers, n, l, m, and ms.) Here PEP is not causing the collapse to stop; it just predicts that it will stop. Lewis claims that the reason this is explanatory is that it falls into the "negative information" category. The reason that the star stopped collapsing is that there was no physically permissible state for it to get into. This is information about its causal history, in that it describes the terminal point of that history.

(2) Explanation of Laws by Laws. Newton explained Kepler's laws (ellipses, equal areas in equal times, p2 = d3) by deriving them from his laws of motion and gravitation (inertia, F = ma, action-reaction, and F = Gm1m2/r2). This is the kind of explanation to which the inferential view is especially well suited (as well as the pragmatic view that we will consider next time), but it does not fit immediately into the causal view of explanation (Newton's laws don't cause Kepler's laws to be true.) That is because the causal view of explanation seems best-suited for explaining particular events, rather than general regularities. Lewis responds to several objections to his theory by saying that his theory does not intend to cover anything more than explanations of events. (Not a good answer as is, since then we would not have a general theory of explanation, but only a description of certain kinds of explanation.) However, he does have an answer at his disposal: one way to give information about causal histories is to consider what is common to all causal histories for events of a given type (e.g., a planet orbiting around a star according to Kepler's laws). Q: Is this enough?

There are of course the other problems mentioned earlier: Salmon's view relies on the notion of spatiotemporal continuous processes to explain the notion of causal processes. (Lewis is not subject to this problem, since he has an alternative theory of causation: linkage by chains of non-backtracking counterfactual dependence.)