Changes

# VP: http://www.cs.nyu.edu/pipermail/fom/1998-February/001248.html

# VP: http://www.cs.nyu.edu/pipermail/fom/1998-February/001248.html

====Oct 2008 : Classical/Constructive Mathematics====

====Oct 2008 : Classical vs. Constructive Mathematics====

* http://www.cs.nyu.edu/pipermail/fom/2008-October/thread.html#13127

* http://www.cs.nyu.edu/pipermail/fom/2008-October/thread.html#13127

===Foreground===

===Foreground===

Harvey Friedman (15 Oct 2008), "Classical/Constructive Mathematics", FOMA

Harvey Friedman (15 Oct 2008), "Classical/Constructive Mathematics", FOMA.

<blockquote>

<blockquote>

I am still in the phase of chasing down links between the various questions and I don't have any news or conclusions to offer, but my web searches keep bringing me back to this old discussion on the FOM list:

I am still in the phase of chasing down links between the various questions and I don't have any news or conclusions to offer, but my web searches keep bringing me back to this old discussion on the FOM list:

[http://www.cs.nyu.edu/pipermail/fom/1998-February/thread.html#1160 Intuitionistic Mathematics and Building Bridges].

http://www.cs.nyu.edu/pipermail/fom/1998-February/thread.html#1160

I find one comment by Vaughan Pratt to be especially e-&/or-pro-vocative:

I find one comment by Vaughan Pratt to be especially e-&and;/&or;-pro-vocative:

Vaughn Pratt (27 Feb 1998), "Intuitionistic Mathematics and Building Bridges", FOMA.

    last twenty years that the logic of the legal profession is rarely Boolean,

    and sometimes even idempotence.  But that aside, excluded middle

    and double negation are the exception rather than the rule.

VP: Lawyers aren't alone in this.  The permitted rules of reasoning

    that go along with whichever scientific method is currently in

<p>It has been my impression from having dealt with a lot of lawyers over the last twenty years that the logic of the legal profession is rarely Boolean, with a few isolated exceptions such as jury verdicts which permit only guilty or not guilty, no middle verdict allowed.  Often legal logic is not even intuitionistic, with conjunction failing commutativity and sometimes even idempotence.  But that aside, excluded middle and double negation are the exception rather than the rule.</p>

    vogue seem to have the same non-Boolean character in general.

VP: The very *thought* of a lawyer or scientist appealing to Peirce's law,

    ((P->Q)->P)->P, to prove a point boggles the mind.  And imagine them

 

    trying to defend their use of that law by actually proving it:  the

<p>The very *thought* of a lawyer or scientist appealing to Peirce's law, ((P&rarr;Q)&rarr;P)&rarr;P, to prove a point boggles the mind.  And imagine them trying to defend their use of that law by actually proving it:  the audience would simply ssume this was one of those bits of logical sleight-of-hand where the wool is pulled over one's eyes by some sophistry that goes against common sense.</p>

    audience would simply ssume this was one of those bits of logical

    sleight-of-hand where the wool is pulled over one's eyes by some

    sophistry that goes against common sense.

Anyway, to make a long story elliptic,

Anyway, to make a long story elliptic, here is one of my current write-ups on Peirce's Law that led me back into this old briar patch:

here is one of my current write-ups on

Peirce's Law that led me back into this

old briar patch:

http://www.mywikibiz.com/Peirce's_law

http://www.mywikibiz.com/Peirce's_law

More to say on this later, but I just wanted to get

More to say on this later, but I just wanted to get a good chunk of the background set out in one place.

a good chunk of the background set out in one place.

==Logical Graph Sandbox : Very Rough Sand Reckoning==

==Logical Graph Sandbox : Very Rough Sand Reckoning==