Tuesday, May 18, 2010

A Depressing Theory of Ceterus Paribus Clauses

We want to say "sugarcubes dissolve in water, ceterus paribus", but what does that mean? Philosophical analysis of the phrase ceterus paribus has proved surprisingly difficult. For example, the quoted sentence doesn't mean that all or most pieces of sugar that actually will be dropped into water will dissolve.

Here's a depressing proposal for how ceterus paribus clauses work. We have a substantive (implicit) theory of what "the normal cases" are like, which is based on human daily life and maybe some random traditions too. We use this when evaluating ceterus paribus sentences to choose which way of making the target sentence true to consider. So, for example, 'ceterus paribus' clauses get filled in so that "dropped eggs break, ceterus parbus" is true, because people tend to hang out in places near the surface of the earth, which don't have thick rugs, so it's part of our substantive theory of what's "normal" that when something is dropped there's a hard surface below it (as opposed to a thick rug, or the empty expanse of space).

1 comment:

  1. I don't buy your theory (or I misunderstand it). Indeed, I think your example is actually a good counterexample.

    It's actually quite probable that in the west we spend the majority of our time in carpeted environments. Indeed, we spend probably 8 hours a day in bed and dropped eggs in bed don't break. Even better consider the statement "Planets have liquid water on their surface." True we know about exceptions but in daily human life we are almost exclusively concerned about the planet earth which does have liquid water on it's surface.

    Ultimately the problem is that being true in normal human experience can't mean "is true in most situations humans experience" or even "is true in a importance weighted average of human experience" as then your account simply comes out false. But if not then you haven't really offered any better analysis than we had to start with.


    I suggest that there are actually two distinct sense in which we use ceterus paribus statements, one of which has a resemblance to your account and the other is quite different.

    The first way we use ceterus parabus clauses is as a justification in some kind of argument. One might say, "The workers died because gaseous chlorine compounds are poisonous," but one need not think that even the most frequently encountered chlorine containing compounds are poisinous. Rather it's simply a way of gesturing at a precise explanation that the audience could fill in themselves if they remain unconvinced. It's the equivalent of saying "triangles have positive area" in a math proof and expecting the reader to fill in the fact that the triangles under consideration aren't the degenerate cases.

    The other time we use ceterus parabus clauses is to instruct someone who is genuienly unfamiliar with something (at least in this context). Here I take us to be giving *practical* advice about what is good to assume.

    We tell people "gaseous chlorine compounds are poisinous" even if most such compounds people encounter aren't because it's the useful assumption to make. In other words we are saying "Unless you have reason to know it's not poisinous treat such a compound as if it is." Similarly we tell kids "dogs have found legs" because it's good for them to assume (absent some defeasing condition) that an unseen dog will have four legs.

    As with your theory this too has an implicit substantive theory of what is normal underneath in the sense that we are advising people to act as if something is true unless something about the situation suggests otherwise. Thus we implicitly have some conception of what situations will be normal and not seem to suggest otherwise.

    Note, however, this account entirely does away with the idea of analyzing ceterus paribus statements as having truth values independent of the understood motivations of the speakers.

    I mean if I'm working in some kind of research facility and someone says to me "Chlorine compounds are poisinous" the implicit statement is that "it's a good rule of thumb to assume such compounds are poisionous to save your live."

    However, if I'm working in the very same facility with the very same compounds but we are desperately trying to fend off a murderous force of guerillas the statement would have a very different meaning. It would instead convey, "It's a good rule of thumb to assume that spraying enemies with these compounds will kill them." It's entierly possible that one would endorse the claim in the first instance and reject it in the second even though the compounds I'm likely to encounter are exactly the same.