If Evidence Neutrality (EN) is true, it is presumably true everywhere. One way to argue against it then is to argue that it doesn’t hold in other subjects. And that’s what Williamson does. He argues that it doesn’t hold in particular in science.

bq. If Evidence Neutrality psychologises evidence in philosophy, it psychologises evidence in the natural sciences too. But it is fanciful to regard evidence in the natural sciences as consisting of psychological facts rather than, for example, facts about the results of experiments and measurements. When scientists state their evidence in their publications, they state mainly non-psychological facts (unless they are psychologists); are they not best placed to know what their evidence is?

If this were a true description of the position of evidence in science, it would be a problem for EN. But it isn’t. EN doesn’t psychologise evidence in science, it _institutionalises_ it. Let’s recall the original statement of EN.

bq. [W]hether a proposition constitutes evidence is in principle uncontentiously decidable, in the sense that a community of inquirers can always in principle achieve common knowledge as to whether any given proposition constitutes evidence for the inquiry. (Emphasis added)

Here’s one way to preserve EN in a field. Adopt some standards for something being evidence in that field, standards that are in practice (if not always in theory) decidable. Then take questions about whether those standards are good standards to belong to another field. That is, take it that people who are questioning the standards, questioning whether these standards genuinely generate evidence, to be outside the community in the sense relevant to EN. They might of course be part of another intellectual community, but they aren’t part of this community. That way we can preserve EN within every given community.

Compare a principle we might call Foul Neutrality (FN) governing a sport. It’s pretty important for playing football that we have a quick method for deciding what’s a foul and what isn’t. And this must be decidable independent of one’s interest in the game. We don’t get FN by psychologising fouls; we get it by having referees. The referees could be wrong, and indeed we could have interesting projects about improving the quality of referees. But when we engage in that project we’ve stopped playing football. The community of footballers (as such) satisfies FN because it’s part of being in that community that we take the referee’s word as final.

Science isn’t like football in that it requires absolute respect of the referees judgment. But it is frequently true that the project of using methods or devices to produce evidence is quite distinct from the project of evaluating whether those methods or devices are good. And we can sensibly individuate communities by looking at which methods they take as given. The short version of my response to this argument is that that’s really how science works; i.e. that science consists of communities so individuated. Each community has a refereeing institution. Or, at least, it is how it works in the vast majority of cases. In cases where the refereeing institutions break down, where there isn’t some other community to serve in effect as referee for your community, then we might have to fall back on psychological states. But EN doesn’t systematically psychologise evidence in science.

We might think that evidence must consist of facts measured rather than something about their measurement, because those are the kinds of things we can submit to statistical testing. But that argument, if it works, proves too much. Williamson’s initial description of scientific evidence was that it consisted of “the results of experiments and measurements”. But that’s ambiguous between two readings. On the first, scientists just state the outcomes of their measurements. That is the kind of thing that you can do statistical analysis on. On the second, they state the results of the measurement, and describe what kind of measurement it is. And that’s, I think, the true reading. At least for results of any interest, you have to describe how you got them, as well as what you got. But you can’t do statistical analysis on a description of a kind of measurement. So it isn’t true that all scientific evidence consists of things you can plug into mathematical equations.

On the other hand, this picture of scientific practice does seem to support the institutional picture of evidence. Why is it that we report the methods as well as the result? One simple answer is that it is settled (relative to the kind of science we’re engaged with) that using that method produces scientific evidence. That’s not to say that the method is beyond dispute. It might be that some other science studies the workings of the very machines that a particular science takes for granted in their operations. It’s merely to say that this science has approved the method in question.

We can see this even more clearly if we look at engineering settings rather than science settings. Imagine we’re working on a bridge construction project, and we need to know the density of some concrete. We’ve got a machine that measures concrete density, so we use it and, assuming the answers are plausible, we’ll take those answers as given. Evidence Neutrality will be ssatisfied because we’ll agree to use the machine. Of course, the only reason we trust the machine is that there is someone, typically someone else, whose job it is to test the machine on a regular basis, and service it, or have it serviced, if it isn’t, and although we might not know the details of how this process works, we’ll have a nice certificate saying the machine is in good condition to use. Now the folks who calibrate machines like this aren’t perfect, so there are other people whose job it is to audit them on a regular basis. And auditors aren’t perfect either, so there will be some body, perhaps a certification body, that oversees them. A positive mark from an auditor only licences a calibrator to approve a machine if the auditor is in turn certified. The board itself may need to be checked, so maybe it will have a board, perhaps including representatives of people like bridge builders who use the machines that we’re all interested in.

The crucial point about this story is that at every stage in the process, EN is satisfied. It is similar, I think, in sciences, though the structure is more fluid. Just which sciences will validate the use of the measurement techniques in other sciences is not as straightforward as in engineering. And the precise boundary between questions that are internal to a given science and questions external to it will change over time. When many questions central to the science start to turn on a particular kind of question about measurement, then those measurement questions may become part of the science. (For instance, if experimental philosophy really takes off, perhaps questions about survey design will be regarded as philosophical questions in the future. More prominently, in recent years questions about the behaviour of satellites have become part of climate science because of the importance of satellites to climate measurement.) But still the broad structure is fairly similar.

The big difference between science and engineering is what happens at the end of the process. The way I described the bridge building case was that eventually, the people responsible for checking the activities of others were the very people (or at least the representatives of them) who were being watched over to start with. That obviously isn’t what happens in science. We don’t check the activities of (say) particle physicists by putting together a board of psychiatrists, nutritionists, economists etc. How might we satisfy EN in basic physics?

Two obvious answers spring to mind. One, either common sense or philosophy tells us that we can take perceptual evidence as given. So even in fundamental physics we can individuate the community in such a way that those who are raising sceptical doubts are doing something else, namely philosophy.

The other answer is that we might take scientific evidence, at the most fundamental level, to be psychological states. Certainly it isn’t uncommon for _philosophers_ of physics to take the role of physical theory to explain our observings. That’s part of why we’ve ended up with such psychologically flavoured interpretations of quantum mechanics, from the Copenhagen interpretation to the many minds interpretation. Perhaps that’s just philosophers bringing in bad philosophical prejudices, but it seems like we _can_ do science respecting EN. That’s because EN mostly is satisfied by the institutional structure of science, and when it isn’t, it doesn’t seem to destroy science to take some evidence to be psychological. So there isn’t an argument from science against EN.

In the previous post we argued that as well as evidence, we need a notion of an unjustified rule that takes us from evidence to conclusion. Some may think that this notion is too obscure, or at least philosophically disreputable to do the work it’s put to. This section is then a discussion of rules that aims to increase their respectability. The idea is obviously not new; it traces back as least as far as Wittgenstein on rule-following, if not back to Carroll himself. And it has links to contemporary epistemology, wherever someone says that there are things we are entitled to assume without argument. But since it is doing so much work here, and since in conversation it has often been the most puzzling aspect of the argument to others, it may be worth saying just a little about what I’m taking rules to be here.

The argument in that section relied on Lewis Carroll’s example involving modus ponens, and that might suggest that modus ponens is the kind of rule that we need. Indeed, it often seems that some philosophers think that it’s the _only_ rule we need. (Many philosophers have said that conditionalisation, which is really just a probabilistic form of modus ponens, is the only rule we need.) I think this example is misleading for four related reasons.

First, modus ponens is a rule of *implication* and what we’re really looking for here are rules of *inference*. We’re looking for rules that tell you what to do with evidence. And what you do with evidence is draw inferences from it. These may not, in any interesting sense, be implications of the evidence.

Second, modus ponens is necessarily truth preserving, and this might be thought to be related to its acceptability. This seems like a mistake twice over to me. It’s arguable (indeed I’ll briefly argue for it presently) that we need some ampliative rules to explain the rationality of induction. And there are necessarily truth preserving rules that we cannot employ without justification. The rule that lets us infer _p and oxygen has atomic number 8_ from _p_ is necessarily truth preserving, but not a rule we could freely employ without independent justification.

Third, modus ponens can be used in suppositional reasoning just as well as in regular reasoning. It would take us way too far afield to investigate this properly, but I suspect some of the rules we’ll look at can’t be properly be used in all suppositions. (Of course some rules of _implication_, at least in some formulations, also have restrictions on when they can be used; think of the restrictions on necessessitation or universal-introduction.)

Fourth, modus ponens might (although this is controversial) be constitutively related to the meaning of the conditional. Perhaps, as some inferentialists believe, the meaning is determined by the acceptability of the rule. Perhaps the meaning directly implies that it is an acceptable rule. If either of those things are true, they aren’t I think things we’d want to generalise to, say, rules for rational inductive inference. (There is obviously a lot to be said here, such as considering what might justify inferences related to logic if not meaning. Many recent papers by Boghossian, Williamson, Wright and others are relevant here. But I’m just going to avoid that issue for today, in large part because I do find it mysterious how to generalise much of that debate from issues about modus ponens to issues about, say, enumerative induction.)

Now all that is just to say what rules are not. Can we say what they are? As noted above, in some ways rules are very familiar. Any time any philosopher claims that we are warranted, or entitled, to, without justification, rely on the deliverances of some source, it seems they are proposing that the inference from _The source says p_ to _p_ is a good rule. So we can take dogmatists about perception (e.g. Pryor’s “The Sceptic and the Dogmatist”) as endorsing a rule that lets us move from _Appears that p_ to _p_ without antecedent justification. And some anti-reductionists about testimony seem to hold that the rule which licences the inference from _I’m told that p_ to _p_ is a good one. So in some ways this isn’t a new idea, it’s just a way of framing an old idea. There are, however, two reasons we might think that this is a good framing. First, it lets us ask some relatively precise questions about the statement of the rules. Second, by thinking about rules as a class, we can formulate restrictions on what could be a rule.

It is harder than one might like to actually state rules that we can or do use. Clearly it isn’t a rule that we can, in every case, infer from _Appears that p_ to _p_; there are illusions, some of which we know about. Nor is it a rule that we can, in every case, infer from _I have observed many Fs in widespread conditions, and they have all been Gs_ to _The next F I observe will be G_; there are gruesome predicates. We could try to incorporate the exceptions into the rule, but a quick glance at how one might do this reveals that it isn’t too attractive, at least as long as we want to have non-trivial rules. Probably we need something different.

In the case of appearance, there is a natural move to make. Instead of a single rule with all sorts of qualifications, we might try to defend the following two unqualified rules.

(A) If it appears to you that _p_, then you have a reason to believe that _p_.

(ND) If you have a reason to believe that _p_, and this reason isn’t defeated, believe that _p_

The conjunction of (A) and (ND) entails Pryor’s dogmatism, although that conjunction is considerably stronger than dogmatism. For example, it entails that appearances that you have reason to believe are deceptive provide some reasons; dogmatism as such is silent on such appearances. But both rules seem at least defensible, even given the existence of illusions. (Of course, if they are good rules, they don’t need a defence. But we can reasonably expect that a good rule won’t be such that we can have good reason to believe it is bad, and (A) and (ND) pass that rule.)

The case of induction is a little trickier, because as soon as we think about the rule a hard question arises. We can only project non-gruesome predicates. Does that mean (a) that the non-gruesomeness of the projected predicates should be an input to inferences licenced by the rule, or (b) that the rule requires no such input, but it only licences inferences when the predicates are in fact non-grue? The latter sounds more plausible; otherwise no one who lacked the concept of a gruesome predicate could rationally make inductive inferences. But it raises tricky questions about using that rule in suppositional reasoning. What if (assuming this is possible) different predicates would be gruesome if _p_ were true, and we are inferring under the supposition that _p_? It isn’t obvious just what restrictions should be put on the use of this rule in a suppositional context. Perhaps those restrictions are quite tight. This has important consquences for arguments for the contingent a priori that assume that we can make inductive inferences in suppositional contexts, such as John Hawthorne’s “Deeply Contingent A Priori Knowledge” and my “Scepticism, Rationalism and Externalism”.

That was all about the nature of rules; we might wonder whether there is anything that we can say about which rules there are. Different ways of thinking about Carroll’s example suggest two different constraints on rules, one more liberal and the other more conservative.

The more liberal constraint is a kind of transcendental consideration. In many cases it seems, at least prima facie, that we can get knowledge from a certain source, but we couldn’t antecedently justify the use of that source. A classic example of this kind of reasoning is C.A.J. Coady’s arguments for against reductionism in testimony. The thought there is that so much of the time the only way we have of checking one person’s testimony is through the testimony of another, that if we weren’t able to take some testimony as basic knowledge, we’d be led to a debilitating scepticism. That seems unacceptable, so we might take such a rule as given.

The more conservative constraint takes more seriously the particular way in which we need a rule to sidestep Carroll’s tortoise. The core problem isn’t just that when we add another premise, one that justifies a particular use of the rule, we need yet more to get to the conclusion. Rather, the core problem is that when we add the kind of premise that could justify the rule, we need another step of the very same rule. Justifying this particular use of the rule doesn’t seem to get us any closer to where we need to be. Perhaps those cases, where justifying a particular use of the rule still requires the rule, are the only cases where there are unjustified rules.

This seems to be a more conservative principle because whenever it obtains, we’ll be able to give a transcendental argument for the existence of a rule. But the converse doesn’t seem to hold. We might justify taking someone’s testimony about being true because we believe them to be generally reliable. We still need a rule saying that it’s good to believe those who are generally reliable, but that doesn’t seem like the same rule. Similarly, we might accept (A) as a derived, and hence justified, rule because the best explanation of our experiences is that they are generally reliable. (Jonathan Vogel has argued for this at length over the years.) We still need a rule saying that we should believe the best explanation of a phenomena, but that doesn’t look like rule (A) again. On the other hand, Hume’s arguments about induction arguably do show that a justification of induction will need to use induction. And a justification of (ND) will, I imagine, still use something equivalent to it. So even on the more conservative conception of rules, they may still be rules.

These are enormous questions, to say the least, so I don’t think this goes close to settling anything. But I hope it’s enough to suggest that we haven’t given up on systematic epistemology once we admit the notion of unjustified rules that justify inferences. And admitting that, which Carroll’s example suggests we must, is enough to sidestep Williamson’s argument against EN.

In chapter 7 of _The Philosophy of Philosophy_, Timothy Williamson argues against the idea that intuitions are a key part of philosophical evidence. Part of his argument is indirect. He thinks the motivation for taking intuitions to be central comes from accepting a principle he calls Evidence Neutrality, and that that principle is false. I rather suspect that isn’t the best reason to take intuitions to be philosophical evidence, but we’ll set that aside here. What we’ll focus on here is whether Evidence Neutrality is true. Here is the initial statement of Evidence Neutrality.

bq. Although the complete elimination of accidental mistakes and confusions is virtually impossible, we might hope that whether a proposition constitutes evidence is in principle uncontentiously decidable, in the sense that a community of inquirers can always in principle achieve common knowledge as to whether any given proposition constitutes evidence for the inquiry.

It seems to me that this is ambiguous between two readings.

• The weaker reading is that it is decidable, by consensus, which propositions are, in principle, evidentially relevant to an inquiry as to whether _p_.
• The stronger reading is that that is true, and it is also decidable, by consensus, in which epistemic direction each piece of evidence points .

I’m going to argue that one of the arguments against Evidence Neutrality, what we might call the argument from extremists, does not tell against the weaker version. I think (though this claim will eventually need defending) that if either version of Evidence Neutrality is metaphilosophically interesting, then the weaker version is interesting. So perhaps that’s all that we need to defend.

Evidence Neutrality (hereafter, EN) is a kind of dialectical conception of evidence (hereafter, DCE). What our evidence is just is what our interlocutors will allow as evidence. On the stronger reading, it is what our interlocutors will take to be evidence for our conclusions. On the weaker reading, it is what they’ll allow as evidence, though they may say one particular piece of evidence, a piece we take to be crucial, is not very strong. And the big question here is whether we should think of evidence dialectically.

It’s certainly true that evidence that is accepted by our interlocutors will be more persuasive in convincing interlocutors. But that’s no argument, at least no immediate argument, for a DCE. It might be that we have quite a lot of evidence that tells whether _p_, and our interlocutors are just mistaken about this. (Everyone makes mistakes.) Relatedly, some people may simply fail to be persuaded by arguments that are rationally persuasive. So we shouldn’t simply confuse which evidence is dialectically effective with which evidence is genuinely good. If we want to defend a DCE, we’ll have to argue for it more carefully than that.

The key point of the last paragraph is that some people will fail to be persuaded by genuinely good arguments. That suggests a problem; couldn’t we have evidence against a position, but just not evidence accepted by the partisans of that position? The simplest examples of this will be positions whose partisans are hostile to the very idea that evidence can tell in favour of anything at all. Here is how Wililamson converts such examples to arguments against EN.

bq. Some scepticism, like scepticism about reason, is so radical that it leaves too little unchallenged for what remains as shared evidence to be an appropriate basis for evaluating the claims under challenge.

The point here is not a new one. David Lewis makes a similar observation in _Logic for Equivocators_.

bq. The radical case for relevance [i.e. dialethism] should be dismissed just because the hypothesis it requires us to entertain is inconsistent. That may seem dogmatic. And it is: I am affirming the very thesis that Routley and Priest have called into question and – contrary to the rules of debate – I decline to defend it. Further, I concede that it is indefensible against their challenge. They have called so much into question that I have no foothold on undisputed ground. So much the worse for the demand that philosophers always must be ready to defend their theses under the rules of debate.

The point Williamson and Lewis make is clear enough. There are certain radical views that (a) we know to be mistaken, but (b) the nature of the position is such that it has, by its own lights, defences against the actual grounds for our knowledge that it is mistaken. Of course its lights are bad lights; our reasons are good reasons. But such positions have partisans. (This is clearer in Lewis’s case than in Williamson’s.) If our only evidence is the evidence they’ll let us share, we won’t have evidence against these positions. And that might suggest we don’t really know the positions are mistaken, contrary to assumption. (There is a fairly strong evidentialist assumption being made here, namely that if we don’t have evidence against such positions, we don’t know they are mistaken. It’s worth thinking through whether that assumption is right, but I won’t do it here.)

I think, however, that this point goes by too fast. Remember that EN and DCE are claims about evidence. They aren’t claims about what we can do with evidence. To see the importance of this distinction, it’s worth recalling Lewis Carroll’s fable of Achilles and the Tortoise. (The points to follow are perhaps familiar from recent work of Paul Boghossian and Crispin Wright. And I’m indebted here to discussions with Crispin. But note that I’m expressly not committing myself to Boghossian’s views about the meanings of the logical connectives.)

Achilles knows _p_, and _p_ -> _q_. He wants to infer _q_. The tortoise says, wait a second, are you sure that’s a good inference? Achilles says he is sure. He’s sure, he says, that (p & (p -> q)) -> q. The tortoise thinks for a second, and then says that that does sound right. Let’s have that as another premise he says. Achilles happily agrees, and then proceeds to infer _q_. The tortoise is still not sure. He wants to know how Achilles is drawing that conclusion. Achilles says he’s sure that if (p & (p -> q)) & (p & (p -> q)) -> q then _q_. The tortoise agrees that looks true, and says it seems like a pretty good premise to have. Achilles tries again to infer _q_, and the tortoise is again worried about why he’s drawing that conclusion. The story continues for a surprising while, with Achilles adding more and more premises, and seemingly getting no closer to overcoming the Tortoise’s worries.

There’s a mundane lesson to be drawn from that, and an exciting lesson. The mundane lesson is that there is a distinction between premises and rules. Indeed, in every axiomatic formal system, we are given both axioms and rules to generate theorems from old axioms/theorems. In some simple systems the only rule might be modus ponens, the rule that Achilles was looking for. In other systems we might need a rule like necessitation, or universal-introduction. But we always need something more than just axioms.

The exciting lesson is that rules aren’t the kind of things that stand in need of rational justification. They are, to put it perhaps in Wittgensteinian terms, things that justify, rather than things that are justified. Here is how we might draw that conclusion. We can imagine the tortoise not as an unhelpful interlocutor, but as our own nagging doubts. Our own inner Descartes, if you like. If the rules have justifications, then we should be able to give them. And if we give them, we can add them as extra premises from which we reason. But this is the key mistake Achilles makes. At some point we need to stop adding premises, and start doing something with the premises. And that can’t always be supported by reasons. For imagine it could. That is, imagine the rule that let us go from A to B could be supported by evidence E. Then we can still ask, what’s the rule that lets us go from A and E to B? Still we’ll need a rule, and perhaps now we’ll be out of evidence. At some point a jump needs to be made without evidence.

So I conclude rules don’t need evidential justification. That’s not to say that all rules are created equally. There are normative standards governing rules, even though they are not supported by evidence. This makes their status quite delicate. As I read him, Gilbert Ryle introduced the idea of knowledge how directly to address this problem. Following rules can’t be simply propositional knowledge, because that leads to a regress. On the other hand, following rules is normatively, even rationally, evaluable. Ryle thought that if we recognise a category of know how, we can steer between these rocks; we can have something that’s a kind of knowledge, the exercise of which can be rational or irrational, but which doesn’t require evidence.

If it isn’t required that we be able to justify our use of rules to ourselves, it doesn’t seem like it should be required that we be able to justify them to our friends. And that in turn suggests that a dialectical conception of rules would be inappropriate. Who cares if our (rational) friends don’t like the rules we’re using? The only way we could make them like them is by offering reasons that our rules are good rules, and by hypothesis we don’t even need to be able to articulate such reasons to ourselves. Perhaps we don’t even need to have such reasons. So a dialectical conception of rules is bad, and more specifically, Rule Neutrality (understood along the same lines as Evidence Neutrality) is bad.

But note that once we ditch Rule Neutrality, we can respond to the extremists that Lewis and Williamson are worried about _without sacrificing Evidence Neutrality_. Here’s my evidence that dialethism is false. If dialethism is true, some contradiction is true. Taking that to be evidence doesn’t violate Evidence Neutrality, because it’s agreed on all sides. From that it follows, by a rule that I properly accept (i.e. reductio) that dialethism is false. Of course, the dialethists don’t buy that rule. But that’s not my problem, since I’m only committed to sharing evidence with them, not sharing rules. If I accepted the strong form of Evidence Neutrality, that might be a problem, because of course the dialethists don’t think this is evidence _against_ dialethism. On the weak form of Evidence Neutrality, that isn’t a problem either.

It’s a little trickier to respond to the reasons sceptic, but I think it can be done, especially if we think about induction. So imagine that I see a lot of Fs that are all Gs, and I see them in a lot of different places etc. I conclude that I have good reason to believe the next F I see will be G. This is a direct inference; there is no mediating premise. If you don’t think so, try to imagine (a) what such a premise could be, and (b) how it could be justified? I think there aren’t good answers to this question, or at least that any answer is less certain than I am in the conclusion. So my frequent observation of green emeralds is sufficient evidence to conclude that I have a reason to believe something, and hence that reasons scepticism is false.

Summing up, I think that Williamson here has run together two similar, but importantly distinct, principles: Evidence Neutrality and Rule Neutrality. I think he’s right that if you accept both, you’ll have thrown away all hope of a good response to certain positions to which there are good responses. So we shouldn’t accept both of those principles. But if we accept that evidence is knowledge, as Williamson does, then we should think that all our evidence requires justification. And we shouldn’t think that our rules do. Since the acceptability of our evidence/rules to our (rational) interlocutors is grounded in this need for justification, it seems that our reason to accept Evidence Neutrality is not a reason to accept Rule Neutrality. So Rule Neutrality must go. And when it does, the argument from extremism against Evidence Neutrality goes too.

There’s a lot to say about rules, and I’ll say a very little about it tomorrow.

In the previous post I mentioned that Williamson clearly opposes in chapter 7 a broadly psychological conception of philosophical evidence. But it isn’t exactly clear just what his target is. At times he seems to be arguing against psychological evidence _ever_ being philosophically worthwhile. For example, consider the following batch of quotes.

bq. “For now I face the challenge of arguing from a psychological premise, that I believe or we are inclined to believe the Gettier proposition, to an epistemological conclusion, the Gettier proposition itself. That gap is not easily bridged.”

bq. “Since psychological evidence has no obvious bearing on many philosophical issues, judgment scepticism is also encouraged in ways that do not depend on the consequence fallacy.”

bq. “In explaining why we have intuitions, analytic philosophy has a preference for explanations that make those intuitions true over explanations that make them untrue, but the justification for that preference remains unclear”

In those quotes his opponent seems to hold the relatively weak view that psychological evidence can (sometimes) be useful evidence for philosophical conclusion. But other times he seems to take his opponent to be the person who holds the much stronger view that only intuitions are evidence. For instance, he says

bq. “One result [of EN] is the uneasy conception many contemporary analytic philosophers have of their own methodology. They think that, in philosophy, ultimately our evidence consists only of intuitions.”

I think it’s hard to believe that’s really a widespread view in philosophy. Does Singer’s argument for vegetarianism rest (even ultimately) on intuitions about the nutritional value of a vegetarian diet? Does the well-known argument from special relativity against presentism rest on intuitions about whether special relativity is true? Nevertheless, Williamson does attribute it to many (unnamed) philosophers. And yet some of Williamson’s arguments seem directed particularly against this position. For instance, he says

bq. “Taken far enough, the psychologisation of philosophical method becomes self-defeating”

And he cites approvingly Joel Pust’s conclusion that it is self-defeating to hold that

bq. “Aside from propositions describing the occurrence of her judgements, S is justified in believing only those propositions which are part of the best explanation of S’s making the judgements that she makes”

Probably Pust and Williamson are right here, but it hardly tells against anything but a strawman version of the psychological view of evidence. Finally, Williamson objects to a version of Reflective Equilibrium that just attempts to get our intuitions into equilibrium with the following argument.

bq. “The reflective equilibrium account, as usually understood, already assigns a proto-evidential role to at least one kind of non-psychological fact. For it treats philosophers as relying on logical relations between theories and intuitions, in particular their consistency and inconsistency.”

The theme again is that we need some evidence other than intuitions, something that should be common ground. (For reasons I’ll suggest in the next post, I’m not sure this is a good argument for that conclusion though.)

We haven’t got very far by trying to characterise what Williamson’s opponent says. Perhaps it is better to look at his positive proposal for what is evidence in philosophy. We get one statement of what that positive conclusion.

bq. “Our evidence in philosophy consists of facts, most of them non-psychological, to which we have appropriate epistemic access.”

That, in conjunction with the quotes above, suggests he is defending the following three theses.

1. Not all philosophical evidence is psychological.
2. Having _p_ be part of your evidence requires appropriate epistemic access to _p_.
3. The intuition that _p_, or the fact that one has that intuition, is weak evidence, perhaps no evidence at all, that _p_.

A position that denied all three of those would clearly be among the targets of Williamson’s chapter. But that would be crazy, since (1) is obviously true. But a position like the one I sketched at the end of the last post, which was neutral on (2) and denied (3), would still seem to be at odds with the bulk of what Williamson says, and I think is meant to be among the positions ruled out by the considerations he raises.

Now such a position does not seem especially related to the sceptical positions that are the targets of sections 3 and 4 of Williamson’s chapter 7. But that’s as things should be. The question of what our evidence is doesn’t immediately settle the question of what knowledge we have. Taking perceptual evidence to be psychological might be a precursor to defending external world scepticism. But it might also be a precursor to adopting indirect realism. Of course Williamson, by accepting knowledge as evidence, has effectively ruled out classical forms of indirect realism, where we know about the world on the basis of purely phenomenal evidence. But that shouldn’t be presupposed here I think. A position that holds that psychological states, or facts about them, are often crucial evidence for us is opposed to the core doctrines of Williamson’s chapter, even if it is also opposed to some of his other opponents.

Chapter 7 of Timothy Williamson’s “The Philosophy of Philosophy” is an extended argument against “psychologising” evidence in philosophy. Before we can evaluate those arguments, it would be useful to get clear on just what it is to psychologise evidence. In this post I’ll say a bit about what that amounts to, and in the next post look a bit more carefully at Williamson’s text to see just what position he is attributing to his opponent.

In some ways the debate Williamson is contributing to is among the oldest in modern philosophy. Consider the following two positions about perceptual evidence, each of which has found many partisans over the last few centuries.

• Perceptual Evidence is Psychological. My perceptual evidence consists in facts about the psychological states I am in when undergoing a perceptual experience. So, for instance, my perceptual evidence might include that I’m visually representing that there is a table in front of me.
• Perceptual Evidence is External. My perceptual evidence consists in facts that I perceive. So, for instance, my perceptual evidence might include that there indeed is a table in front of me.

The psychological theory has a number of advantages. It can explain how people having illusory perceptions can get the same kind of evidence (albeit of lower quality) as people having veridical experiences. It arguably staves off certain kinds of doubts about our evidence, at least to the extent that we have privileged access to our psychological states. It explains the fact (if it is a fact) that when we get evidence in favour of some proposition _p_ about the external world, we generally know what kind of evidence we have. It is unusual, that is, to get evidence that _p_, but not know whether that is visual evidence, or tactile evidence, or testimonial evidence, or whatever. If the evidence for _p_ just is the visual or tactile or testimonial experience, that is easily explained. And it offers the prospect of an easy theory of evidence possession; a point I’ll return to below.

But there’s one big cost of the psychological theory: it seems to promote scepticism. There is a long tradition, starting in the modern period with Descartes, of proponents of the psychological view wondering how to get from psychological evidence to knowledge of the external world. And there is another long tradition, culminating at the present with Williamson, of opponents of the psychological view using this worry as a reason to start with evidence in the external world, and avoid this sceptical doubt.

The debate here is not confined to perception. We can have a similar debate in testimony. Imagine I am told that _p_ by a trusted friend. I now have some evidence for _p_. What is it? One answer, similar in spirit to the psychological answer above, is that I’ve been told that _p_. Another answer, similar in spirit to the external answer, is _p_ itself. The latter answer might be favoured by a theorist of testimony who thinks that when I get testimony from a trustworthy source, I simply receive the warrant they have for believing _p_. (The two answers here aren’t quite equivalent to the positions known as reductionism and anti-reductionism in the epistemology of testimony. Someone might be an anti-reductionist and hold that the telling, rather than what’s told, is the evidence, by holding that we don’t need any extra grounds to infer, on the basis of that evidence, that _p_. I’ll say more about such inferential rules in later posts.)

Both answers here are possible, but it is much more plausible to take the evidence to be the telling rather than what’s told. So we can use that as a relatively clear example of what happens when we take evidence to be something that supports an external world proposition _p_, rather than _p_ itself. One consequence is that in reporting inferences, we can replace testimonial knowledge with knowledge that the testimony was made without making the inference worse. So imagine we know that if Celtic win today, they’re champions, and we’re told by a trusted friend that Celtic did indeed win. Then we might make either of the following inferences.

An inference from facts about football

1. If Celtic won, they are champions.
2. Celtic won.
3. So, Celtic are champions.

An inference from facts about testimony

1. If Celtic won, they are champions.
2. My friend said that Celtic won.
3. So, Celtic are champions.

The first is valid, while the second is not. But we are interested here in inferences, not implications, so that’s no disqualifying mark against the second inference. For the second has a virtue not shared by the first, namely that its premises are more secure. So it looks like the two inferences are equally good. And that suggests that the second inference really is just making explicit the inference that’s underlying the first.

We’ve now said enough to set up the interesting debate about philosophical evidence. Often we say things like _Intuitively, that’s a cause of that_, or _Intuitively, that’s wrong_ and so on in philosophy. What kind of evidence are we appealing to here?
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Some papers and stuff happening around the web.

• Errol Lord on non-indexical relativism
• Kenny Easwaran on the a priority of computer proofs
• An updated version of my Attitudes and Relativism
• A PDF version of the new version of Deontology and Descartes’ Demon
• Slides from a lecture on Intuitions and Philosophical Evidence

The theme of the lecture was that the case Williamson makes in _The Philosophy of Philosophy_ against evidence being psychological states isn’t as strong as it might at first appear. I’ll be spelling out the themes of that in several blog posts over the next few days.

*Update*: I should add that many of the ideas in the lecture on evidence, and in the upcoming posts, came from conversations here at Arch{e’}, and especially a reading group on _The Philosophy of Philosophy_. The meeting on chapter 7 of the book, which I’m mostly writing about here, was led by “Daniele Sgaravatti”:http://www.st-andrews.ac.uk/~arche/members/member?id=sgaravatti, and his comments were especially useful.

The Inter-University Workshop on Philosophy and Cognitive Science at the “University of Zaragoza”:http://en.wikipedia.org/wiki/University_of_Zaragoza features work by and on an important philosopher. The workshop in May next year will be on my (once again) colleague Ernie Sosa, and I imagine it will be very good. Here’s the actual announcement.

bq. The XIXth edition of the Inter-University Workshop on Philosophy and Cognitive Science will be held on May 18 and 19, of 2009, in Zaragoza, Spain, organized by the Department of Philosophy of the University of Zaragoza. The invited speaker will be Ernest Sosa, Board of Governors Professor of Philosophy at Rutgers University. In recent years Interuniversity Workshop invited speakers have been: A. Clark, M. Davies, D. Dennett, J. Fodor, F. Dretske, R. Millikan, T. Burge, J. Searle, J. Kim, C. Peacocke, F. Recanati, B. Stroud, J. McDowell, N. Block, and P. Carruthers. Professor Sosa’s published or forthcoming work takes up a broad range of issues in epistemology, such as foundationalism/coherentism, internalism/externalism, reliabilism, contextualism, skepticism, the Pyrrhonian problematic and the problem of easy knowledge, epistemic normativity, intuitions and their place in philosophy, epistemic agency, epistemic virtue or competence, the epistemology of disagreement, testimony and social epistemology, the nature of knowledge, and the value of knowledge. The Organizing Committee invites contributions based on topics related to that work. (Some of it is available for downloading at “his website”:http://web.mac.com/ernestsosa/Site/Welcome.html.) Extended drafts (not less than 2000 words) should be sent to the coordinator of the workshop, “Jesús Ezquerro”:mailto:jesus.ezquerro@ehu.es, before February, 27, 2009 (e-mail only). Authors of accepted papers will have their accommodation, but not travel, expenses covered.

I’m in St Andrews now, visiting Arche, and while it’s been a lot of fun, and very rewarding intellectually, it’s been hard work! I’d hoped it would be a relaxing break with lots of blogging, but that hasn’t quite worked out. Anyway, here are three things I’ve been working on.

• I’ve updated “Deontology and Descartes’ Demon”:http://brian.weatherson.org/DDD.doc (Warning: Word Doc) to (a) take account of some objections that were made, and (b) get it into the right form for the Journal of Philosophy. The latter was hard work: they won’t let you use contractions and I can’t write without them! The former was more fun.
• I’ve written five lectures on probability in philosophy – “1”:http://brian.weatherson.org/PL1.pdf, “2-3”:http://brian.weatherson.org/PL2.pdf, “4-5”:http://brian.weatherson.org/PL4.pdf, and given four of them. I don’t have all my books/papers here, so some of the references to what other people say was from memory. So if I’ve misrepresented you, my apologies in advance. (I mostly got around this shortcoming by not talking about particular people much at all, just making sweeping generalisations about what lots of people think. So there are a few things that could be given better citations.)
• Various people (most notably Crispin Wright and David Chalmers) have been pressing me on one of the core assumptions in “Moderate Rationalism and Bayesian Scepticism”:http://brian.weatherson.org/MRaBS.pdf, namely that you can’t learn p by getting evidence that decreases its probability. I’d like to have a good response to their worries, and if I did so I’d be putting it here. The worries are specifically about cases where p is a disjunction, and the evidence raises the probability of one disjunct, but decreases the probability of the other. Hopefully soon I’ll have thought of something clever to say here, but for now I don’t have much to say of any use.

This week I’ll be at the “Language and Law”:http://www.csmn.uio.no/events/2008/lang_law.xml workshop at the University of Oslo, and I’m hoping to have lots of interesting things to report back from that.