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    • Why should we grade final exams?

      Lucky-jimAre students aware that most of their professors can accurately predict their final grades prior to the final exam or paper? Is this just hubris on my part, or do people in the biz long enough get very good at this?

      If it's not hubris, then it raises a genuine practical ethics problem. If I already know what the student is going to make, why do I feel morally obligated to grade the paper? I can't figure this out.

      I'm clearly obligated by prudence to grade the papers as the LSU hair and teeth men* would be very unhappy with me for not doing so. But would they be right to be unhappy?

      Maybe the problem is that if the students knew I wasn't grading their final papers, then they wouldn't do the work. So perhaps not doing the grading would involve deception? This seems pretty weak to me though. I could just not say anything one way or the other, or honestly say that I might** grade the person's exam or paper. Knowing their exams might be graded would motivate them enough.

      A few students want comments on their work and we owe them that, but the overwhelming majority of them don't. So why not just hold onto the papers and grade them later if a student wants comments?

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    • Is the Barwise/Etchemendy system unsound?

      I might be being an idiot here, but I can't for the life of me figure out how the following inference is disallowed in the Barker-Plummer/Barwise/Etchemendy textbook:

      1. Ex(Rax)

      2. ExEx (Rxx)   1, E introduction

      This is clearly invalid, because there are anti-symmetric relations (note that if it were valid one can prove ExEx (Rxx) from ExEy (Rxy), and that ExEx(Rxx) has the same truth conditions as Ex(Rxx)).

      Intuitively, Existential Introduction should be restricted so that one cannot replace a name or eigenvariable with a variable that is already bound in the sentence. But I can't find this restriction in Barker-Plummer/Barwise/Etchemendy. My friend couldn't find it in the old red Mates book either, so we think it's not unlikely that we're both missing something obvious.

      I turned to the soundness proof in Barker-Plummer/Barwise/Etchemendy and they leave the case of Existential Introduction as an excercise to the reader. It has a little star next to it showing that it is a difficult problem. I'm wondering if it's impossible. But, again, it's more likely that I'm missing something, so if anyone who teaches from the book could take a look my introductory logic students would appreciate it.

    • If fighting climate change denial is like fighting creationism, how do we do it?

      Helen De Cruz has some excellent suggestions for how to talk to creationists given that neither debate nor denouncement are likely to be productive.  She describes the way in which a religious person who is not a creationist can speak to another religious person who is a creationist, e.g., by pointing out that Biblical literalism is a recently emerged approach, one that may be impossible to apply consistently, and for that reason among others it may not be thoroughly used by anyone.

      This article by Dan Kahan suggests that disbelief in human-caused climate change is like belief in creationism in this respect: What people "believe" about each doesn't reflect what they know, but rather expresses who they are.  This supports the thesis that providing evidence for creationism isn't likely to change minds and that providing evidence for climate change isn't likely to change minds, either.

      But what is the climate change equivalent, where we speak to people from their own perspective as Helen proposes that we do for religious people who are creationists?

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    • On Pernicious Philosophers

      There’s a discussion going on over at Leiter about the results of his latest poll: which modern philosopher had the “most pernicious influence” on philosophy?  Heidegger was the strong #1, both in terms of the number of people who hated him, and the intensity of their hatred.  This doesn’t seem that surprising, given that Leiter’s readers, um, lean analytic and since Leiter took their Derrida option off the table.

      Much more interesting, it seems to me, is the historical skew of the results.  Most of the figures in the top 20 are 20th century philosophers, and all but three (Descartes, Berkeley, and Kant) are 19th or 20th century (and it wouldn’t be conceptually wrong to put Kant in with the 19c).  Does this reflect poor historical training?  Do influential but controversial positions get absorbed into the ‘mainstream?’

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    • Brazilian music on Fridays: ‘Palco’

      This week I am posting ‘Palco’, a 1981 song by Gilberto Gil. The other day I was reminded of this song and then showed it to my daughters; they now love it, especially the part at the beginning that goes ‘my soul smells like talcum power, like a baby’s buttocks’ (‘minha alma cheira a talco, como bumbum de bebê'). It’s a great song, even if betrays its 1980s-ness in the instrumental overproduction. But it’s upbeat and lively, so perfect to put ya’ll in the mood for the weekend.

      (BMoF will be on recess next week.)

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    • Commenting on the Blog

      Should be working again!  Thanks for everyone's patience while we've been having problems with Typepad.

    • More on the Fermi paradox (from David Wallace).

      In a comment to the previous post on the Fermi Paradox, David Wallace wrote this terrific exposition of it.  I agree with almost everything he says, so I will save my own quibbles for a comment.  David writes:

      Just to clarify the force of the Fermi paradox (which is intended to rest on quantitative factors, not just a general "where are they?"), here are the main basically-uncontroversial premises that get it going:

      1. The Galaxy contains an awful lot of stars, and plenty of them have planets. There are 100+ billion stars in the Galaxy, and in our neighbourhood, around 5% of them are G-type stars like the Sun in non-binary systems. Our best theories of planet formation make planets look generic, and the current era of exoplanetology backs that up. I think it would be very hard now to argue for fewer than several hundred million Earth-type planets, and that's almost certainly a significant underestimate.
      2. The Galaxy is much older than it is large. The Galaxy is something like 100,000 light years across. But it's nearly ten billion years old, which is to say that light could have travelled across the Galactic disk and back some 50,000 times.
      3. Slow interstellar travel (c.0-1%-1% of light speed) is technologically possible. Pioneer 10 is already a starship, travelling at (1/30,000) of the speed of light, and that was by accident. There are a quite large number of designs and plans for spacecraft capable of reaching between 0.1% and 10% of light speed. That we are unlikely to build any of them any time soon – the mission time is too long and the cost is currently rather painful – isn't my point; the point is that this kind of speed is borderline possible with *current technology*, let alone the extrapolated capabilities of much-more-advanced civilisations. (Contrast relativistic starflight, which doesn't violate any known physical principle but isn't remotely possible with any feasible technology we can think of now; contrast faster-than-light starflight, which actually looks *physically* impossible.)
      4.  Self-replicating intelligent machinery is technologically possible. We have an existence proof for this: humans. (I guess I can't absolutely rule out some strange principle of emergent engineering which makes it physically impossible to make a slow-moving space probe capable of carrying machines (humans or not) that can reproduce the probe even though self-replicating intelligence and probes are separately possible, but it seems ad hoc.) Given 2-4, it is technologically possible for a civilisation to send physical vehicles to every solar system in the Galaxy in a timescale *much* less than the age of the Galaxy. (Err on the pessimistic side: assume 0.1% light-speed propulsion and a 1000-year turnaround time; you still get an expansion wave moving at 0.05% of lightspeed, enough to span the galaxy in 200 million years, or 2% of its current age. Why might a civilisation do so? Several plausible reasons: (i) colonisation. As Allen Olley points out, this isn't a plausible way to move your existing population (I don't really agree with Eric's resource-based argument for colonisation) but it is a plausible way to spread your civilisation, or your species, across the Galaxy. (ii) exploration. Robot probes is a really great way to explore space, as we've found ourselves. (See the Wiley paper cited above.) (iii) malevolence or prudence. People very often react by noting that each of (i)-(iii) is speculative, and maybe intelligent civilisations don't tend to do that kind of thing. Fair enough. But the crucial issue in the Fermi paradox is that *it only has to happen once*. And unless life *basically never* evolves, or intelligence *basically never* evolves, or civilisations *basically always* die off before they get to the stage of exploring the galaxy, there ought to have been so many civilisations that it seems implausible that not even one would do this. (Note that I'm pretty sure *we* would do it, if we got to the point at which it was reasonably inexpensive.) An illustration: suppose life only turns up on 1% of earth-type planets, and that intelligence only evolves in 1% of biospheres, and that 99% of civilisations wipe themselves out through war or resource exhaustion before reaching the stage when it's feasible (indeed relatively cheap) to spread across the Galaxy. Then, on a pretty conservative estimate of 1 billion habitable planets, there should have been 1000 suitable civilisations so far in Galactic history. Yet *not even one* decided to try the explore-the-galaxy strategy? Things get several orders of magnitude worse when you consider that the strategy works perfectly well over intergalactic distances too, and that there are hundreds or thousands of galaxies in realistic exploration range. Could they be here but not be noticed? Well, it's quite hard to hide a decelerating starship, but maybe none happen to have turned up recently. There could be all manner of things hiding in the Solar System. But again: does *every single* civilisation behave that way? It seems unmotivated to suppose so. (Unless there is a single hegemonic species or coalition that requires it coercively.) I think the force of the Paradox is this: yes, for any given civilisation we can imagine reasons why we could be completely oblivious of it despite it being millions of years older than us and quite capable of having spread across the Galaxy. But unless technological civilisations are fantastically unlikely to arise on a per-planet basis, there should have been such an enormous number of them by now that it becomes really implausible that *none of them* have done so.

    • Fighting creationism through debate is pointless; how then can we do it?

      A friend of mine is doing her DPhil in Oxford. She's American, and out of term she goes back to her home in middle America. She recently went to see the newly refurbished museum in her home town. When she was looking at the displays on human evolution, a museum guard, who had been observing her, suddenly said "So, what side are you on: the Bible or evolution?" Whereupon my friend replied "What do you mean what side am I on? This is not a football game, you know".

      I am deeply troubled by the incipient creationism, which treats biblical literalism as a serious intellectual contender to scientific inquiry. I want my children to grow up with normal biology textbooks, not with Of Pandas and People. If creationists win their lobbying efforts to make creationism mainstream in schools and the public sphere, that is a loss for everyone (including the creationists). Debates don't seem to do any instrumental good. If we are not going to fight creationism through debates, how can we – as public intellectuals – ensure that creationism doesn't encroach even further upon our schools and public life?

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    • SB 1391 and the Criminalization of Pregnancy in Tennessee

      A petition is circulating online asking Gov. Bill Haslam to veto SB 1391.  The bill would modify the Tennessee criminal code to allow for criminal assault charges to be brought against women who use illegal narcotics while pregnant, should their drug use lead to harm or death for the fetus or child.  These charges carry a penalty of up to 15 years in prison.  But the bill is so badly written, it could affect all pregnant women in Tennessee, whether or not they use drugs, should something go wrong during their pregnancy.  In effect, SB 1391 threatens to criminalize pregnancy in Tennessee. 

      Policy analysts and political commentators across the world have voiced their concerns with SB 1391, arguing that it could have far-reaching consequences (Reality Check, The Guardian, The New York Times, The Daily Beast, and NPR).  Even some pro-life groups recognize that SB 1391 could incentivize abortions for women who use drugs, since women risk up to 15 years in prison by continuing their pregnancy, especially if they are unable to access drug treatment programs (All Our Lives).  

      If we really want to support the flourishing of children in Tennessee, then we need to move beyond the pro-life/pro-choice framework to seek reproductive justice for everyone, based on “the right to have children, not have children, and to parent the children we have in safe and healthy environments” (SisterSong).  For example, rather than punishing women who use illegal drugs while pregnant, we should be extending the Safe Harbor Act to support women who use either prescription drugs or non-prescription drugs to get the treatment they need, and to stay clean for the sake of their families and themselves. 

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    • Talk like Shakespeare day

      Mark, 'tis 'Talk Liketh Shakespeare Day!' Then come, good fellows, and let us dream of dragons and finless fish, take but a moment and speak of clip-winged griffins and a ramping cat. The youth of England are on fire, and though men may sleep, some have knives with edges. Such words as his delight the eyes and fill the mind as the secret parts of fortune come to a handsome gentleman, as a stratagem to its quarter returns an ill-shaped fish with magnanimity! If you disagree, you are a stuffed cloak-bag of guts, a bolting-hutch of beastliness!  (h/t David Hoyt)