Epistemic Value

Monday, May 26, 2008

New Closure Principle

We're in marking season at the moment, that most glorious time of year. The gloom is punctured from time to time by really awful exam scripts that make daft assertions. My colleague Jesper Kallestrup was marking a bunch the other day and came across this gem that I thought I'd share with you:

"According to Duncan Pritchard, Closure is the principle that if P knows Q, and Q entials R, then R knows P too."

It looks as if I've somehow single-handedly invented a new closure principle!


  • At 12:51 PM, Anonymous Jim said…

    Well, let's see. I know Jesper, and Duncan knows me, so that must mean Jesper entials Duncan. Cool.

  • At 3:21 AM, Blogger Clayton said…

    I can't think of a counterexample, can you?

    So, nice work Duncan?

  • At 9:05 PM, Blogger Duncan Pritchard said…

    You know Clayton, you're right--I'll recall the script and make sure this student gets a First!

  • At 7:25 PM, Anonymous Muhammad said…

    thanks very much for sharing!

  • At 7:59 PM, Blogger j. adam carter said…

    If Jesper knows Duncan, and Duncan competently deduces Jesper from Campbell, then Campbell is Jesper! This is all becoming clearer!

  • At 2:11 PM, Anonymous Anonymous said…

    "Closure is the principle that if P knows Q, and Q entails R then R knows P too"

    Duncan - "as well" or "also" would be better english.

    I will publish my counterexample next week.

    Nice try though!

  • At 2:52 PM, Anonymous Anonymous said…

    If "B" knows "W", and "W" completely seduces "B" from "A", then "A" is "B"?

    Sounds more like a soap opera to me...

    S. Kidder


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