Spooky coincidence? I think not

Today in Logic I talked about vagueness and the sorites paradox. Then when I get back to the office, I find that this Saturday, Alan Saunders on The Philosopher’s Zone has a program on – you guessed it – the sorites paradox. Is that a spooky coincidence or what?

No, it’s not spooky. It’s just a coincidence.

Anyway, from the little outline, it’s clear that Saunders has a more adept journalistic sense of what can get a point across than me. His example (is Bruce Willis bald? Peter Garrett definitely is, and Billy Connolly definately isn’t, but what to say of Bruce?) is much nicer than my boring examples of strips of colour shading from red to yellow, or heaps of grains of sand or the other stock philosophical examples…

Regardless, the class had a pretty energetic discussion, from people trying on different responses to the paradox, to other students pushing pretty hard on the “just stop doing logic if it produces problems like this” sort of line. I like these sort of questions – at least if they’re attempts to get to grips with the issues, as they seemed to be to me – because they’re a sign that when you do something like logic, it’s our job to address the philosophical or interpretive issues of what is going on. This is why I like doing the sorites paradox and vagueness around halfway through an intro course, as it gets to the heart of the issue of what we’re doing when we talk about truth values and the machinery of classical propositional logic.

However, after the class, it wasn’t clear to me if I did a very good job of addressing the issues that came up in the discussion. So, my readers, it’s with some trepidation that I’m going to point you to the lectures for the subject. They’re recorded and can be found online (at least, until next year when they’ll be overwritten or archived or somesuch). If you can bear it (and have nothing better to do for 50 minutes or so), take a listen to the March 28 recording here. Here are the disclaimers.

  • The recording starts with me asking if anyone has a nine volt battery. The wireless microphone was dead, and needed a new battery. A nice person from Teaching Space Services delivered the battery just as the lecture started.

  • I’m writing on the whiteboard. The people there can see it but you can’t. I wrote down the form of a sorites argument, discussed in the last class (setting a series of colours, each apparently indistinguishable from the next, shading from what looks to red to what looks to yellow), what makes the thing a paradox (the premises seem true and the conclusion seems false and the argument seems valid), and some options for responding to the tension of the paradox.

  • There are a number of questions from the class (good questions), but they don’t all get picked up from the recording.

  • I sound terrible but that might just be my reaction to hearing my own voice.

Anyway, if you’re interested in the issue, or if you want to give me some feedback on this class, listen and post here. If you are a 161-115 student (I know some of you read this thing) please feel free to post comments too. I’m up for getting tips on teaching. Especially on dealing with questions from the floor. I wasn’t happy with how I dealt with all of the student questions, so tips and comments will be most helpful.


I’m Greg Restall, and this is my personal website. I am the Shelby Cullom Davis Professor of Philosophy at the University of St Andrews, and the Director of the Arché Philosophical Research Centre for Logic, Language, Metaphysics and Epistemology I like thinking about – and helping other people think about – logic and philosophy and the many different ways they can inform each other.


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