Philosophy of Science
Theses Possibly or Actually Attributable to van Fraassen
I will attempt to identify and comment on a few main theses from among the many van Fraassen advances in his article "The Pragmatics of Explanation."
Explanation is a Pragmatic Phenomenon
What does that mean, exactly? Well, in linguistics and the philosophy of language, pragmatics deals with phenomena that are context dependent. In particular, it deals with sentences whose meanings depend on the context in which they are uttered. If I say "Every molecule of water contains two hydrogen atoms," it makes no difference when I say it, or where I say it, or even whether I say it or you do; it means the same thing regardless of these contextual factors. By contrast, the sentence "I am here now" means something different if I say it than if you do, if I say it now than if I say it ten minutes from now, and if I say it here or somewhere else.
van Fraassen is saying that something similar is true of explanations. Whether something counts as an explanation depends on the context in which the explanation is requested and offered. If this is right, then when we have tried to analyze explanation by considering phenomena and asking whether a proposed explanation succeeds in explaining them or not, we have been making a false assumption, namely that there are straightforward facts about this. We can't answer these questions without providing information about the context in which the explanations are requested and offered; to try to say whether something counts as an explanation without information about the context is like trying to say to whom the word 'I' refers without saying who is using it.
Explanation is a Three-Place Relation
This is really just a different way to make the previous point. Explanation has traditionally been thought of as a relation between a theory and a fact: a theory either explains or doesn't explain a particular fact, period. van Fraassen thinks that this is a mistake. Rather, explanation is a three-place relation between a theory, a fact, and a context: a theory explains a fact relative to a particular context. In other contexts the same theory might not explain the same fact. [SI p. 156]
Effects of Context 1: The Contrast Class
Why did P occur? Because C.
van Fraassen suggests that one thing we need to know in order to evaluate C as an explanation of P is what the contrast class for P is. Implicit in the context will be a set of things that did not occur, and to ask why P occurred is ask why its alternatives did not occur. But in different contexts, the same question might have different implicit contrast classes. Why did the mayor get paresis (when most citizens of the city did not)? Because he had syphilis. In this case, "Because he had syphilis" seems explanatory, because it tells us a property of the mayor that the other citizens did not have and that makes his probability of getting paresis higher than theirs. Why did the mayor get paresis (when his syphilitic buddies did not)? With this different contrast class, "because he had syphilis" is no longer explanatory, since his buddies had the same odds of getting paresis that he had.
Effects of Context 2: The Relevance Relation
This may be a little trickier. And van Fraassen certainly is vaguer about it. His pragmatic view of explanation is modeled to some extent on formal pragmatics in philosophy of language (and linguistics). But there, there are clear and precise rules to determine how context affects content. If a context is a triple of a possible world, an individual, and a time, then 'now' refers to the time of the context, 'I' refers to the individual of the context, 'here' refers to the location of the individual in the world at the time, and so on.
We don't have anything that precise to determine the contrast class or the relevance relation. But it's still a useful notion. The relevance relation determines which causal factors are salient in a given context. An excellent example here is the one van Fraassen quotes from Hanson (SI 125):
the cause of death might have been set out by a physician as 'multiple haemorrhage', by the barrister as 'negligence on the part of the driver', by a carriage-builder as 'a defect in the brakeblock construction', by a civic planner as 'the presence of tall shrubbery at that turning'.
It is the relevance relation which vF thinks accounts for the asymmetries of explanation. He thinks that these asymmetries are not intrinsic, but context-relative; in some contexts the asymmetry may be the reverse of what it is in other contexts. (That's the point of the "Tower and the Shadow" short-short story.)
Science Contains No Explanations
This is van Fraassen's most dramatic assertion. The idea is that science is concerned with describing the causal structure of the world, but not with determining which parts of that structure are salient. (This is also closely related to van Fraassen's reasons for his anti-metaphysical "constructive empiricism," which we will consider later in the course.)
A related point is that vF does not think that explanatory power is a reason to think a theory is true, nor is it a reason to choose one theory over another. All that is required of a scientific theory is that it be "empirically adequate."
[By the way, my title is meant to allude to Kierkegaard's Concluding Unscientific Postscript, which has a section entitled "Theses Possibly or Actually Attributable to Lessing." Uh, for what it's worth.]