Recent Compass Articles

Server Errors

Apologies to anyone who couldn’t get at the site for the previous hours. There was a server error. I’ve now fixed it, I think, and the site should be running. There are some details below the fold for anyone interested in that kind of thing.

Continue reading “Server Errors”

A Priori Workshop

My colleague Greg Currie is organizing a workshop on the a priori, to take place here in Nottingham on October 9th.  Further details here.  Please contact Greg if you would like to attend.

The workshop is timed to coincide with the visit of Nottingham Special Professor Michael Devitt, whose forthcoming volume Putting Metaphysics First includes some work (check out the title of essay 13) attacking the a priori (a popular pastime of late).

There is such a thing as being too cautious…

In his very interesting paper at the Rutgers Epistemology Conference, Higher-Order Evidence (PDF), David Christensen discusses a lot of cases where, in the process of investigating whether p, we learn something about our ability to detect whether p. In the primary cases Christensen discusses, we first come to believe p, then come to believe that our capacities are impaired in some way. And one of the epistemologically interesting questions is what we should do at this stage. I wanted to consider a slightly different question.

S is investigating a murder. She gets evidence E, and on the basis of that quite reasonably concludes that it is quite likely the butler did it (her credence in that is 2/3), a serious possibility that the gardener did it (her credence in that is 1/4), and very little chance that neither did it (her credence in that is 1/12).

S then is told, by a usually reliable source, that she has taken some drug that leads to people systematically underestimating how strongly their evidence supports various propositions. So if someone’s taken this drug, and believes p to degree 2/3, then p is usually something that’s more or less guaranteed to be true by their evidence.

What should S do?
Continue reading “There is such a thing as being too cautious…”


Some stuff you might not have seen from around the web.

  • Elsevier publishes fake journals. Henry Farrell has some suggestions for what to do about it.
  • Alva Noe has an article about drugs in sport, focussing on why it is that we worry about some enhancements but not others. I think Alva is a little too dismissive of the health concerns; I wouldn’t care about steroids at all if they weren’t dangerous. More realistically, I wouldn’t care if a player with cancer took steroids as part of a standard cancer treatment. But it is interesting to think about where we draw the moral lines, and about what that says about what we value in sporting performance. And the terminology here is bizarre – if we cared about all ‘performance enhancing drugs’, presumably we’d want to get rid of the Gatorade in the dugout.
  • Jacob Ross has a fascinating paper on Sleeping Beauty and Countable Additivity (PDF).
  • This list of cities with the highest quality of life is interesting, but I think they’re not rating things I care about if Perth comes well ahead of New York.

Trusting Experts

I imagine the following point is well known, but it might be news enough to some people to be worth posting here. The following principle is inconsistent.

Trust Experts. If you know there is someone who is (a) perfectly rational and (b) strictly better informed than you, i.e. they know everything you know and know more as well, whose credence in p is x, then your credence in p should be x.

The reason this is inconsistent is that there can be multiple experts. Here’s one way to generate a problem for Trust Experts.

There are two coins, 1 and 2, to be flipped. The coin flipping procedure is known to be fair, so it is known that for each coin, the chance of it coming up heads is 1/2. And the coins are independent. Let H1 be that the first coin lands heads, and H2 be that the second coin lands heads.

The coins are now flipped, but you can’t see how they are flipped. There are sixteen people, called witnesses, in an adjacent room, plus an experimenter, who knows how the coin lands. Using a randomising device, the experimenter assigns each of the sixteen different propositions that are truth-functions of H1 and H2 to a different witness, and tells them what their assigned proposition is, and what its truth value is. The witnesses know that the experimenter is assigning propositions at random, and that the experimenter always tells the truth about the truth value of propositions. So the witnesses simply conditionalise on the truth of the information that they receive.

Consider first the witnesses who are told the truth values of (H1 v T2) and (H1 v ~T2). One of these will be told that their assigned proposition is true. Whoever that is, call them W1, will have credence 2/3 in H1.

Consider next the witnesses who are told the truth values of (~H1 v T2) and (~H1 v ~T2). Again, one of these will be told that their assigned proposition is true. Whoever that is, call them W2, will have credence 1/3 in H1.

So if you were following Trust Experts, you’d have to have credence 2/3 in H1, because of the existence of W1, and have credence 1/3 in H1, because of the existence of W2. That’s inconsistent, so Trust Experts is inconsistent.

More on the NIP

For the curious, this prospectus gives details of the (institute provisionally known as the) Northern Institute of Philosophy, which will come into existence in Aberdeen this September.