The Rules of Thought: Philosophy and the a priori

I'm going to live up to the blogger stereotype and set a few posts on autofocus. The shameless project is to make the case that you might have good reason to read The Rules of Thought, the book that Benjamin Jarvis and I recently wrote. (OUP catalogue page) (my webpage)

I think that there are three possible hooks into our project. One of them -- the one that represented our own way into the project -- concerns the epistemology of the a priori in general, and the epistemology of philosophy in particular. Ben and I trace this interest pretty specifically to 2005, when, while PhD students at Brown, we took Joshua Schechter's seminar on the a priori, and also attended Timothy Williamson's Blackwell-Brown lectures, which eventually became The Philosophy of Philosophy. We were attracted by traditional idea that in many paradigmatic instances, philosophical investigation proceeded in some important sense independently from experience, but came to appreciate that (a) there were deep mysteries concerning the explanation for how this could be, and (b) there were strong challenges that suggested that the traditional idea couldn't be right. For example, the traditional idea has it that judgments about thought experiments constitute appreciate of facts that are both a priori and necessary; but Williamson gave what is now a somewhat famous argument that this can't be so: thought experiments don't include enough detail to entail the typical judgments. So the best they can support is something like a contingent, empirical counterfactual: if someone were in such-and-such circumstances, he would have JTB but no K, etc.

We wrote a defensive paper in response to Williamson's argument, explaining how one can understand the content of thought-experiment judgments in a way that renders them more plausibly necessary and a priori, invoking the notion of truth in fiction. ("Thought-Experiment Intuitions and Truth in Fiction" -- (draft) (published)) That paper did two useful things: it gave an objection to Wiliamson's treatment, and it defended a traditional aprioristic picture from Williamson's particular critique. But on the latter score, it was purely defensive; it did little to explain how a priori justification or knowledge was possible, or to articulate just what apriority could consist in. Another paper, "Rational Imagination and Modal Knowledge," (d) (p) gave a bit more epistemological background, and a focus on modal epistemology in particular. By the time of that paper, we were underway on the book.

What we needed, we realized, was a much fuller story about apriority, including detailed engagement with extant critiques of the notion. We give this in Part II of The Rules of Thought. Some of the critiques -- in particular, some of those from Williamson and Hawthorne, as well as some similar challenges from Yablo and Papineau -- show that a characterisation of apriority in terms of more psychological states like knowledge and justified belief is extremely difficult, perhaps impossible. (Here's a related blog post from last year.) Our general characterisation of the a priori is a negative one, given in terms of propositional justification. A subject has a priori propositional justification for p just in case she has justification for p, and this isn't due in constitutive part to any of the subject's experiences. We explain how this approach avoids the challenges to the a priori that are in the literature, and argue that there is strong reason to think that philosophical investigation is often a priori in our sense. The focus on propositional justification requires a fairly strong version of the traditional distinction between warranting and enabling roles for experience, which we attempt to explicate.

The negative characterisation is thin by design. We are explicitly open to a kind of pluralism about apriority, according to which various positive epistemic states can realise apriority. The state we focus on most is what we call 'rational necessity' -- certain contents are, we think, by their nature such that there is always conclusive reason to accept them. (Much more on this idea in another post on another motivation for the project.) But we allow that other states may realise apriority as well; we are open, for example, to the idea that it is a priori that perception is generally reliable, even though this isn't rationally necessary. Perhaps some kind of pragmatic explanation for these a priori propositions may be found.

In the context of our theory of the a priori, and our more detailed positive story about rational necessity, we rehearse the main ideas from our two previous papers on philosophical methodology: thought-experiment judgments, properly understood, often have contents that are rationally necessary, hence a priori; so likewise for many judgments in modal epistemology concerning what is metaphysically possible. This all happens in Part II of the book.

So that's the first hook for our book: understanding the a priori and the epistemology of philosophy. We tell a story that is able to vindicate a number of pretty traditional ideas about how philosophy works (but without problematic focus on words or concepts). The other two hooks will each get another post -- one concerning Fregean ideas about mental content, and one about the role of intuitions.

Motivating a 'Hybrid' Epistemology

I guess I ought to make a point of announcing on my blog that my book with Ben Jarvis has finally been published. (That's UK only at the moment; it'll be worldwide later this month.) Here's OUP's official page. There were some delays with the printing that pushed things back a month or two longer than expected, but on the whole, I'm very pleased with the experience we had with OUP.

One of the central themes in The Rules of Thought is that there is an important sense in which the norms of rationality are objective: they apply universally to all thinkers, regardless of the subjects' rational limitations. We're motivated to say this in significant part because of cases of 'blind irrationality' -- situations where subjects fail with respect to rationality, in a way in which no intuitions or inclinations alert them to their error. There is an important sense in cases like this in which these are genuine failures of rationality; therefore, in this sense, the demands of rationality are not relative to the subject's limitations. The subject is doing the best he can do, given his limitations. This motivates us to the fairly strong view that for 'rational necessities' -- roughly, those truths that someone might want to call 'analytic' or 'conceptual' or maybe 'a priori' -- subjects always have conclusive reason to accept them. That is, everyone always has propositional justification for all of these truths. For example, my grandmother has propositional justification for every arithmetical truth. This is surprising to many, but Ben and I have arguments in the book that I think really do show that this has to be right.

But there is a puzzle that comes from this way of setting things out. It's a puzzle that's brought out really nicely in this new paper by Sharon Berry, "Default Reasonableness and the Mathoids." (Her target isn't views like ours, but the intuitions she's trading with are poignant for us.) We think that complex arthmetic truths -- Fermat's Last Theorem, for instance -- are always propositionally justified in the same way that simple ones -- 1+4=5, for instance -- are. But if this is right, it's not straightforward to make sense of the intuition that simple arithmetical premises are legitimate starting places in proofs in a way that complex arithmetical premises are not. Berry's central thought experiment involves the Mathoids, who find Fermat's Last Theorem (or other complex truths) immediately, primitively compelling in the way that we find simpler truths. She observes that it's intuitive that their proof method is unjustified, but argues that it's hard to find a principled difference between them and us. This seems to me exactly right.

The solution Ben and I have been thinking about -- this is discussed briefly in the book, and at greater length in a paper we're working on -- is that we need a 'hybrid' epistemology. We're still convinced by the arguments mentioned above that there must be an important epistemic element that doesn't depend on any of the contingencies of human psychology. To this extent, we're committed to the falsity of a thoroughgoingly virtue epistemology according to which epitsemic competences are the only fundamental epistemically normative element in town. But the virtue story also has something importantly right: the story we tell about propositional justification can't be the whole story either. The messier, psychology-laden doxastic justification story can't be given entirely in terms of propositional justification. We need to say something more contingent, about how the belief is formed. Virtue epistemology seems promising -- we want to say that there are virtuous traits and vicious traits, with respect to believing what is propositionally justified, and that these make a difference for doxastic justification and knowledge. The challenge, of course, is to describe in what these virtues consist. (If you want to distinguish us from the Mathoids, reliabilism is a clear non-starter.)

We have some tentative ideas for how this might go, but I'll save them for later. The main point of this post is to suggest that there's strong reason to think we might need two independent stories here: one for 'pure' epistemic statuses like propositional justification (the minimalist story that is a main theme in our book) and one for 'impure' epistemic statuses that bring in the psychology (the virtue story we're thinking about now). Neither will do on its own.

Williamson on Apriority

Here's an argument with the conclusion that there's no deep difference between cats and dogs.

The Dogs and Cats Argument. Although a distinction between cats and dogs can be drawn, it turns out on closer examination to be a superficial one; it does not cut at the biological joints. Consider, for example, a paradigmatic cat, Felix. Felix has the following properties: (i) he has four legs, fur, and a tail; (ii) he eats canned food out of a bowl; (iii) humans like to stroke his back. Now consider a paradigmatic dog, Fido. Fido has all three of these properties as well. For instance, Fido also has four legs, and fur, and a tail, and when he eats, it is often served from a can into a bowl. And humans like to stroke Fido's back, too. In these respects, Fido and Felix are almost exactly similar. Therefore, there can't possibly be any deep biological distinction between them.

I'm sure you'll agree that the dogs and cats argument is terrible. Put a pin in that and consider another argument.

In his contribution to Al Casullo and Josh Thurow's forthcoming volume, The A Priori in Philosophy, Timothy Williamson argues against the theoretical significance of the distinction between the a priori and a posteriori. The thesis of the paper is that "although a distinction between a priori and a posteriori knowledge (or justification) can be drawn, it is a superficial one, of little theoretical interest."

It's a somewhat puzzling paper, I think, because it's not at all clear how it's broad argumentative strategy is supposed to support the conclusion. Williamson does not, for instance, articulate what he takes the apriority distinction to be, then argue that it is theoretically uninteresting. Instead, he identifies certain paradigms of a priori and a posteriori knowledge, then emphasizes various similarities between them. For example, he argues that the cognitive mechanisms underwriting certain a priori judgments are similar in various respects to those that underwrite certain a posteriori judgments. Then he spends most of the rest of the paper arguing that these are not idiosyncratic features of his particular examples. But why is this supposed to be relevant?

Williamson writes:

The problem is obvious. As characterized above, the cognitive processes underlying Norman's clearly a priori knowledge of (1) and his clearly a posteriori knowledge of (2) are almost exactly similar. If so, how can there be a deep epistemological difference between them?

But I do not find this problem at all obvious. The argument at least appears to have the structure of the terrible dogs and cats argument above. The thing to say about that argument is that identifying various similarities between two things does practically nothing to show that there aren't deep differences between them. There are deep biological distinctions between cats and dogs, but they're not ones that you can find by counting their legs or examining how humans interact with them. Similarly, Williamson offers nothing at all that I can see to rule out the possibility that there is a deep distinction between the a priori and a posteriori, but it is not one that is manifest in the cognitive mechanisms underwriting these judgments. For as Williamson himself later emphasizes, there's more to epistemology than cognitive mechanisms. If apriority lives in propositional justification—which is where I think it lives—then there's just no reason to expect it to show up at this psychological level. That doesn't mean it's not a deep distinction.

That Williamson's argument needs to be treated very carefully should also be evident from the fact that prima facie, it looks like it has enough teeth to show that the distinction between knowledge and false belief is not an epistemically deep one—a conclusion that everyone, but Williamson most of all, should reject. For the cognitive processes underlying cases of knowledge are often almost exactly similar to those underlying false beliefs. Should this tempt us to ask how, then, there could be a deep epistemological difference between them? I really don't see why.

Where does apriority live?

Here are some things that can be violent:

• Neighborhoods
• People
• Actions

Violence inheres in these different kinds of things in different kinds of ways. A violent person is liable to punch you in the face if provoked; that the neighborhood will never punch you in the face doesn't count against its violence. Still, it's not like there's not a general category, violence, that applies in some sense to violent neighborhoods, violent people, and violent actions. These things are certainly connected somehow or other.

When you have this kind of set-up, you can sensibly ask which kind of entity is the best candidate for a more fundamental bearer of the property. To put it a bit colorfully: where does the violence live? Although I can imagine some people disagreeing, it seems to me pretty plausible that the violence of a neighborhood is explained by the violence of the people who populate it, rather than vice versa. Violence doesn't live in neighborhoods. And what makes a violent person? It seems to me that it has something to do with a propensity to perform violent actions. On this way of answering the question, violence ultimately lives in actions. But maybe not, maybe there's no real way to understand a violent action independently of the violent character traits that make a person violent. Maybe violence ultimately lives in people, or in character traits. I'd be curious to hear arguments about this interesting question. It's not my area.

But my area has some similarly interesting questions, too. Consider apriority. Here are some things that can be a priori:

• Knowledge
• Justification of beliefs
• Justification for beliefs

If you believe in apriority, it's worth spending a bit of time thinking about where the apriority lives.

Casullo on Negative and Positive Approaches to Apriority

Chapter 1 of Al Casullo's book, A Priori Justification, explores various theories of a priori justification. In the penultimate step of the chapter, he's argued that the motivations behind various theories ultimately converge on two views -- one 'negative', and one 'positive'. This is from p. 31 (with his labels changed for simplicity):

• (Neg) S's belief that p is justified a priori if and only if S's justification for the belief that p does not depend on experience.
• (Pos) S's belief that p is justified a priori if and only if S's belief that p is justified by some nonexperiential source.

Thus stated, the negative characterization (N), Al says, is ambiguous, because of different ways in which justification can depend on experience. So (N) is disambiguated into:

• (Neg-Weak) S's belief that p is justified a priori if and only if S's belief that p is nonexperientially justified.
• (Neg-Strong) S's belief that p is justified a priori if and only if S's belief that p is nonexperientially justified and cannot be defeated by experience.

Of the three remaining views -- Pos, Neg-Weak, and Neg-Strong, Al goes on to claim that there are really only two, because Pos and Neg-Weak are equivalent. The rationale here seems to be the idea that  every justified belief has its justification due to a source, and any given source is either experiential or nonexperiential. Take a justified belief, and consider the binary question of whether its justification's source is experiential; Neg-Weak says yes if it is; Pos says no if it isn't.

But I think this bit of reasoning is too quick. I'm suspicious of the move from nonexperiential justification to derivation from a nonexperiential source. To equate Pos with Neg-Weak is to legislate in advance that for any justified beliefs, there is a source of its justification. That is to say, it assumes prior to argument that there is no original justification -- justification that does not depend on a source. But that there is such original justification is, it seems to me, a coherent view that occupies a spot in logical space. (For what it's worth, I also think it's true; Ben and I defend it in The Rules of Thought.)

Sources generate things that weren't already there. The assumption that justification for a priori justified belief must derive from a source is, I think, part of the motivation for supposing there must be some kind of faculty of intuition to serve as source.

I'm not sure whether there are nonexperiential sources of justification. But I'm firmly committed to beliefs that are justified in a way that doesn't depend on experience. If these two attitudes are jointly coherent, then Casullo is wrong to equate Pos with Neg-Weak.