When is vagueness a virtue in science?

Like a lot of people, I think precision is a virtue in science. One sign of scientific progress is increasing precision, often but not necessarily expressed mathematically. For instance, Darwin got a lot right without using any math–but we’ve since learned a lot more about evolution than we could have otherwise by expressing Darwin’s ideas more precisely and mathematically. Or think of how the vagueness with which ecologists define “biodiversity” and “ecosystem function” leaves us vulnerable to critical scrutiny. Or think of how Bob May’s math undermined and corrected previous verbal intuitions about how “diversity” or “complexity” might relate to “stability” in ecology. Thereby forcing future ecologists working on that topic to quit waving their arms and instead say exactly what they meant. We need math because the consequences of our assumptions often can’t be worked out without math, and because our choice of words often misleads us in subtle but important ways. Some profound scientific ideas can’t even be expressed verbally, at least not without doing the math first.

So in the spirit of being contrarian with myself,* here’s a question: can vagueness rather than precision ever be a virtue in science? Vagueness is sometimes inevitable, such as when some new idea is first being developed. But is it ever desirable, so that we wouldn’t want to get rid of it even if we could?

Some smart people would say yes. For instance, here’s philosopher Ken Waters**, writing in 2013 about vagueness in the definition of “gene”:

What about biologists? What do they say when repeatedly pressed by philosophers to answer the question, ‘What is a gene?’ In my own experience, after being shown that their answers are vague, admit exceptions, or are ambiguous, biologists typically shrug their shoulders. Many quickly concede that they do not know exactly what a gene is. Reflective biologists add that trying to answer the question with the kind of rigor that philosophers demand would be
counterproductive. Progress in genetics, they say, has depended and continues to depend on “muddling through”. Science, they insist, would be stymied if geneticists were forced to agree on using a clear and unambiguous concept of the gene.

The example of “gene” hints at one kind of situation in which vagueness might be a good thing: some bit of biology is messy and complicated. There’s a range of cases that are obviously similar in important ways, but that also differ in various ways and it’s hard to pin down exactly which similarities and differences matter for what purposes. So rather than risk pinning them down in the wrong way, we muddle through with vague definitions. Although personally, I might describe such cases as cases in which vagueness is inevitable rather than advantageous. Or to put it another way, in such cases the greatest level of precision possible or reasonable may not be all that precise in an absolute sense (Peter Godfrey-Smith recently wrote about this in an evolutionary context). Put still another way, it’s not as if we ever want as much vagueness as possible–there’d be no point to defining genes as “molecular thingies that do stuff”. So whether you want to say vagueness is good rather than merely unavoidable probably depends on what baseline you’re comparing it to. I’d say the same about other vaguely-defined terms in ecology and evolution, like “species” and “ecosystem”.

It occurs to me that the best example of a usefully-vague term in ecology might be…[wait for it!]…”ecology”. Ecologists all share some interests, and it’s good for all of us to recognize those shared interests, even though they’re quite vaguely defined. Recognition of shared interests encourages us to see each other as colleagues involved in a shared intellectual project that’s worth pursuing. But if you tried to define those shared interests more precisely, you’d either end up with an empty definition (which is just vagueness by another name), or you’d end up with a definition sufficiently precise as to exclude some people whom everybody considers ecologists. I’m thinking for instance of Cooper’s The Science of the Struggle for Existence, a philosophical work framed around a search for the definition of ecology. As I recall, the definition Cooper ends up with basically defines ecosystem ecology as not ecology. I’m also thinking of various people who’ve defined ecology as “scientific natural history”, or otherwise emphasized the primacy or centrality of natural history or field work to ecology, in a way that defines me and Ben Bolker out of the field (I’m sure that wasn’t the intent***, but that’s the effect). Tyler Cowen has noted that many political unions and other partnerships are based on “creative ambiguity”.**** Perhaps the field of ecology is one such union.

Another way vagueness can be useful is by allowing an idea to draw greater interest and more research effort than it otherwise would. If progress depends on having a critical mass of people working on a problem, and if defining the problem too precisely (at least initially) would discourage lots of people from working on it, then maybe vagueness is a good thing. Of course, you can have too much of any good thing–a vague idea that attracts a lot of research interest is a good way to start a bandwagon.

One important distinction here is between vaguely defined concepts, and concepts that have various precise but contrasting definitions. As noted earlier in the post, “stability” is now an example of the latter, having previously been an example of the former. I don’t think it’s ever helpful to mix up different definitions of stability, or be vague about which definition you’re using. More broadly, I suspect there are various ways scientific ideas can be vague, and it’s probably important to distinguish between them. Maybe somebody needs to write the scientific equivalent of Seven Types of Ambiguity.

*For which this is the best illustration, given my credentials as a zombie fighter. 🙂

**A conversation with whom got me thinking about this. And as an aside, if you’re looking for philosophy of science to read and you’re interested in genetics and evolution, you should add some of Ken’s stuff to your reading list.

***At least I hope not! 🙂

****Such as academic departments. As Cowen writes:

We find the same in many academic departments.  Things can be going along just fine, but once the department has to write out an explicit plan for future growth and the allocation of slots across different fields or methods, all hell breaks loose.