The argument from the good lot

I have uploaded the slides from my second Pittsburgh lunchtime talk. This is an initial presentation of a current paper project. Here is the question: If science proceeds by (1) proposing a number of candidate explanations for a phenomenon, (2) ranking these explanations by explanatory power and (3) accepting the most highly ranked of the candidates, then why should we expect science to arrive at truth? After all, it is always possible that we simply failed to consider the true hypothesis in the first place. This would explain why so many successful — that is, highly ranked — past theories were later abandoned. In recent years this issue has been vigorously pursued by Kyle Stanford, who speaks of the “problem of unconceived alternatives”. In my talk I develop an account of why the problem of unconceived alternatives is not acute in much of the life sciences. More to follow.

How to think new thoughts

Much of science is a kind of puzzle solving activity. You, the scientist, are presented with a phenomenon whose causes and underlying mechanisms we do not yet understand — and your task is to elucidate them. That this succeeds at all inspires awe. That it succeeds fairly regularly and efficiently requires an explanation.

There are two issues to be understood, broadly speaking: (1) how we can tell that a scientific hypothesis is probably true (this is usually called “justification”) and (2) how we come up with hypotheses in the first place (usually called “discovery”). Both stages are crucial. The best tester of hypotheses is helpless if she has nothing to test. And the most creative hypotheses are of limited use if we cannot assess their truth. Importantly, the efficiency of science must depend to a large extent on discovery: on the fact that candidate hypotheses can be produced quickly and reliably.

Not so long ago, philosophers of science believed that discovery is mostly intractable: a matter of happy guesses and creative intuitions. In recent decades, however, it has been argued that systematic insight into scientific hypothesis generation is possible. A particularly nice and approachable example of this type of thinking in the philosophy of biology is given in a recent book by Carl Craver and Lindley Darden (based on their earlier research). They argue that scientists invent new mechanisms by using three main strategies: (1) they transfer mechanisms schemata from related problems (schema instantiation); (2) they transfer mechanism components from related problems (modular subassembly); (3) they investigate how known components or interactions can link up (forward/backward-chaining). A somewhat broader and more historical (but less problem oriented) perspective is given by Jutta Schickore in the Stanford Encyclopedia of Philosophy.

In a new paper, I and my co-author Kärin Nickelsen present our own contribution to the discovery debate. Our work is in the Craver/Darden tradition, but we look in detail at two historical cases — Oxidative Phosphorylation and the Calvin-Benson cycle — to advance the state of the art a bit (by about a paper’s worth). We focus on three areas:

First, we consider “hard cases” of discovery from the history of sciences. By this we mean achievements of acknowledged originality that no one would describe as mere extrapolations of previous knowledge. If a particularly spectacular scientific discovery can be explained in terms of a certain set of discovery strategies, then this speaks to the usefulness and power of these strategies: less complex cases should present no problem to them. So hard cases help our claim that much of scientific creativity is ultimately explicable in terms of the skillful and diligent use of basic heuristics.

Second, we are interested in whether discovery strategies are “substrate neutral” or “domain specific”. Are there general rules for discovering scientific hypotheses, or do strategies only apply to particular fields of inquiry — or even to particular kinds of empirical problems within disciplines? We think that the truth is for once in the middle: discovery strategies seem to be somewhat general, but they need to be applied to highly domain-specific previous knowledge. We discuss instances of this in the paper.

Third, the existing literature does not pay enough attention to the way in which the space of possible hypotheses is explored systematically. In one of our cases, for instance, a particularly interesting scientific hypotheses was arrived at — in part — by simple causal combinatorics. It was known that two types of events, A and B, were correlated. This allowed the following (exhaustive) set of hypotheses to be explored: Does A cause B? Does B cause A? Or do A and B have a common cause? While this procedure may sound simple, its results are anything but.

The paper has just appeared in History and Philosophy of the Life Sciences, and our penultimate draft is available on Pitt’s PhilSci archive.

The limits of my language and the limits of my world

Mcwhorter coverThe Language Hoax by John H. McWhorter is a book about the Sapir-Whorf hypothesis: the notion that languages deeply affect the way in which their speakers conceptualize the world. To give a few examples, Russian makes a distinction between lighter blues and darker blues that English (like German and French) doesn’t make. Do Russian speakers therefore have a richer perception of blue than English speakers? Similarly, German and French assign genders to objects, which may lead German speakers to assign male qualities to tables (sturdy?) while French speakers assign feminine qualities to them (supportive?). More interestingly perhaps, the male gender is somewhat dominant in European languages: for instance, the third person plural in French is “ils” even if there are women in a group. So does this lay the conceptual basis for a kind of sexism? As a final example, it is certainly plausible (and fun) to speculate that speakers of languages without a future tense might conceptualize the future, and plan for it, in a way that is completely different from our own. Thus, the potential reach of the Sapir-Whorf hypothesis is vast: it ranges from the relatively innocuous (color perception) to the socially charged (gender roles) to the conceptually profound (our very notion of time).

In this brief but rich book, McWhorter argues that the available empirical evidence speaks against any strong version of the Sapir-Whorf hypothesis. True, Russian speakers can distinguish certain shades of blue more quickly than speakers of other languages — but the differences are small in absolute terms.1 Yes, we can spin tales about the impact of linguistic peculiarities on cultural traits in some subpopulations: for instance, McWorther discusses attempts to link obligatory “evidential markers” (I see/I hear/they say) with particularly skeptical attitudes towards knowledge. However, he shows that this correlation breaks down (like many similar ones) when we extend our data set to a larger sample of languages and cultures: we then find cultural skepticism in languages without evidential markers and evidential markers in cultures with little skepticism.2 Now, such counterexamples are not conclusive: consider that the counterexamples could be explained by the fact that evidential markers sometimes cause a particularly skeptical attitude, and that there could be alternative causes of skeptical attitudes. But the counterexamples certainly show that any strong assumptions about language “structuring” thought are doubtful. The main point is that it is easy to come up with “just so stories” that link linguistic habits and cultural traits,3 but we need demonstrations of actual causality and deep cognitive effects. According to McWhorter, the consensus among professional linguists is that such demonstrations have not succeeded; language does have an impact on cognition, but these effects are relatively weak.

In addition to the empirical and methodological points, McWhorter argues that many in the humanities are drawn to the Sapir-Whorf hypothesis for the wrong reasons. The inclination is to think that demonstrating the richness of foreign linguistic concepts is to counteract a kind of Western cultural hegemony. But of course this can backfire if we find that there are some quite nifty things for which Western languages seem to be better equipped than others. For instance, the English language marks the hypothetical and counterfactual more explicitly than Mandarin Chinese. So do the Chinese have an impoverished sense of the hypothetical? If you are worried about Western cultural hegemony, you won’t find this thesis attractive. McWhorter takes the view that the Whorfian approach is the wrong way to argue for human equality. We should instead recognize the essential similarity of all human thought — which just happens to be expressed in different linguistic forms:

We are told that what languages teach us about being human is how different we are. Actually, languages’ lesson for us is more truly progressive – that our differences are variations on being the same. Many would consider that something to celebrate. (p. 168)

I certainly do.

Aside from its linguistic interest, the Sapir-Whorf hypothesis has a relationship to a topic in the history and philosophy of science (and this is why I, as a tradesman, was initially interested). Namely, it touches on the question of scientific realism: should we trust scientific results about unobservables such as “electron” or “gene”? McWhorter does not discuss this aspect of the story, but I believe it is worth some thought. I suspect that to many people, especially in the humanities, the question of scientific realism seems almost beside the point. This is because they “know” that even our ordinary perceptions — such as the color “blue” or activities like “eat and drink”4 — are deeply structured by our language. So how could the much more distant objects of scientific investigation not be similarly affected by our linguistic and conceptual apparatus? But of course, if McWhorter is correct that the Sapir-Whorf hypothesis fails for ordinary perception, then its extension to scientific results cannot even get off the ground.

  1. I also suspect that if we were to look at this data, we would find that the differences between populations are not only small in absolute terms, but small relative to the variation within populations.
  2. One of my favorite examples in the book is of a culture (the Amazonian Jarawara and related societies) where the feminine, rather than the masculine, is the default form for most words and plurals. However, the culture is nevertheless quite misogynistic.
  3. In Our Time just did an episode on Rudyard Kipling.
  4. Some languages do not distinguish between ingesting solids and liquids and have one word to cover both activities; others make fine-grained distinctions between ingesting different kinds of solids (hard, soft, stringy, round, …). The wealth of examples in this book is worth the price of entry.

There is no cow on the ice

Here at the Center for Philosophy of Science we are gently encouraged to express what we are thinking about on glassboards outside our offices. I think this is 1) a terrific idea and 2) not entirely unlike an accidentally acquired Tumblr that you have to keep feeding. My glassboard has been a bit stale for the past month, and so others have risen to the challenge of updating it:

IMG 7202

I still don’t get the hammer joke (I’m sorry, it just doesn’t hit the nail on the head). But ingen ko på isen — this is good to keep in mind.

John Norton has blogged about some more glassboard art.