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As the question asks, what are the most successful responses to van Fraassen's "bad lot" argument against explanatory inference?

By 'successful' I just mean most widely accepted or argued for. Or perhaps just the most famous.

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The bad lot objection

Inference to the Best Explanation [henceforth, IBE] is a form of uncertain inference that has us infer the truth of a hypothesis from the judgment that that hypothesis proffers the best of the available, competing potential explanations of the evidence. Few uncertain inference forms hold as much intuitive plausibility and wide applicability to actual human reasoning as IBE. IBE arguably constitutes the dominant mode of inference at work in cases of human reasoning ranging from medical diagnosis to forensics to auto repair; and conclusions reached by IBE within these fields tend to be above reproach. Nonetheless, philosophers have found reasons to doubt the general cogency of IBE. If there is one objection in particular that is most commonly believed to put into doubt IBE's merits as an inference form, it is the so-called "bad lot objection". Bas van Fraassen (1989, pp. 142-143) gives the classic statement of this objection:

  • [IBE] selects the best among the historically given hypotheses. We can watch no contest of the theories we have so painfully struggled to formulate, with those no one has proposed. So our selection may well be the best of a bad lot. To believe is at least to consider more likely to be true, than not. [...] For me to take it that the best of set X will be more likely to be true than not, requires a prior belief that the truth is more likely to be found in X, than not.

Stated in other words, van Fraassen's criticism is that the value of any inference to the best explanation will be constrained by that of the lot of considered hypotheses. If this lot does not include a true hypothesis, then IBE will inevitably recommend to us a false belief. There are any number of hypotheses that could potentially explain the evidence in question, more than we could plausibly be expected to consider or even think up in the first place. But then the true hypothesis may be one of the countless explanatory hypotheses that we are not presently considering. IBE presumes a collection of hypotheses to be considered; it does not involve any inference to such a collection. As such, it gives us no reason to think that we are not starting off with a bad lot (a collection of explanatory but false hypotheses). Consequently, it can hardly be trusted as a reliable inferential vehicle for attaining true beliefs. (Jonah N. Schupbach, 'Is the Bad Lot Objection Just Misguided?', Erkenntnis (1975-), Vol. 79, No. 1 (February 2014), pp. 55-64 : 55-6.)

Objection to the objection

In my view Jonah N. Schupbach, 'Is the Bad Lot Objection Just Misguided?', just cited, offers a cogent riposte to van Fraassen. It is, I'd say, one of the most successful responses. And, to keep to your criteria, tt takes one of the most widely argued for lines of resistance.

My answer to the bad lot objection turns on the basic distinction between the form of an inference and the material content that we bring to the inferential table whenever our reasoning actually instantiates an inference form. The form of an inference is, loosely speaking, a general pattern that the inference instantiates and which it shares with other inferences; the material content includes the particular statements, concepts, etc. used to instantiate an inference form, thereby producing an inference. To take a simple example, which is all we will need for the sake of this paper, a particular inference may go as follows:

Either Bill is drunk or he's stupid.

Bill isn't stupid.

Therefore Bill is drunk.

The pattern or form that this inference most clearly instantiates is that of disjunctive syllogism:

Either p or q

Not-q

Therefore p

And the material content that this instance of disjunctive syllogism brings to the table includes the specified premises and conclusion ("Bill is drunk or he's stupid", "Bill isn't stupid", "Bill is drunk") along with the concepts expressed therein.

We may, of course, apply this same distinction to IBE. A particular instance of this inference form might go as follows:

It's late at night, and Bill has just come home; he's bumbling about, knocking things over, and he cannot pronounce a single word without slurring.

Among the available, competing explanatory hypotheses {h1: Bill is drunk, h2: Bill has very recently developed a cognitive disorder, h3: Bill is pretending to be drunk}, h1 proffers the best potential explanation of Bill's behavior.

Therefore Bill is drunk.

The pattern or form that this inference most obviously instantiates is that of IBE:

e

Among the available, competing explanatory hypotheses {h1,h2,....hn}, h1 proffers the best potential explanation of e.

Therefore h1

And the material content that this instance of IBE brings to the table includes the specified premises and conclusion, along with all of the concepts expressed therein. In particular, this material includes the lot of hypotheses to be considered. In no sense are the particular hypotheses to be considered part of the inferential form; the lot of hypotheses to be considered manifestly changes between IBE's instances.

With this distinction in mind, van Fraassen's objection can be rephrased as the worry that since the form of IBE does not give us any reason to think that we have brought good material content to the inferential table, it cannot be trusted as a reliable mode of inference at all. Phrased in the way, it is unclear why anyone would suppose that the bad lot objection poses a problem for IBE specifically. The objection is not of particular relevance to IBE; one can run such an objection to any form of inference whatever, be it nondeductive or deductive. If, for example, one brings a "bad lot" of premises to the inferential table, then modus ponens will likely commend to us a false conclusion. Moreover, modus ponens itself provides us with no reason to believe that we will instantiate it with true premises. The same point holds for any inference form: by virtue of their formal character, they provide us with few constraints on the quality of the material that may be used to instantiate them on any occasion. But when working with bad material content, virtually any inference form will likely commend a false conclusion.1 Seen in this way, van Fraassen's objection merely points to the garbage in/garbage out, abstract character of all forms of inference. If the bad lot objection causes trouble for IBE, it causes trouble for all inferential forms. (Jonah N. Schupbach, 'Is the Bad Lot Objection Just Misguided?', Erkenntnis (1975-), Vol. 79, No. 1 (February 2014), pp. 55-64 : 57-8.)

  • Brilliant! I was actually looking for a copy of that paper and requested it from the author but he hasn't gotten back to me yet. I recall that in the abstract he says that as well as showing that the objection holds for all inferences if it holds for IBE, he talks about why he thinks it doesn't hold for IBE, or something along those lines? – Joe Lee-Doktor Oct 21 '18 at 21:05
  • And, out if interest, since you said this is "one of" the most successful responses, would you tell me what other responses you think are good? Unless that was just a figure or speech or something. – Joe Lee-Doktor Oct 21 '18 at 21:09
  • I wouldn't see this as an objection but just a unavoidable limitation on the power of abduction. – PeterJ Oct 22 '18 at 11:16
  • I think that's Schupach's point. It's vF who sees it as an objection. – Geoffrey Thomas Oct 22 '18 at 12:12
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    @Joe Lee-Doktor. My quotations from the article omit as you would expect Schupbach's full argument. I have added three further references but I really do prefer Schupbach. Best - Geoffrey – Geoffrey Thomas Oct 22 '18 at 12:23

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