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Re: Cardinality: a definition

Subject: Re: Cardinality: a definition
From: "Jesse F. Hughes"
Date: Sat, 30 Sep 2006 07:14:05 -0400
Newsgroups: sci.math
"MoeBlee" <jazzmobe@xxxxxxxxxxx> writes:

> Yes, I understand that the absence of the axiom of regulairy is not the
> adoption of the negation of the axiom of regularity. So I mentioned the
> negation of the axiom of regularity indeed because it's a stronger
> condition (regarding the question we're dealing with) than just not
> having the axiom of regularity.

Most theories of anti-well-founded sets go further than just negating
the axiom of foundation (or regularity, if you prefer).  They assert
something about what anti-well-founded sets exist.  Aczel's axiom
says, essentially, that for every set of equations of appropriate
form, there exists a unique solution (and then we identify solutions
to distinct sets of equations up to bisimilarity).

See Barwise & Moss's /Vicious Circles/ for an introduction.

-- 
"Quincy, would you rather do epistemology or conceptual analysis?"
"You know what?  I'd rather fight on an aircraft carrier....  And Mama
and Baba (Papa) would fight on an aircraft carrier, too."  
                           -- Quincy P. Hughes, age 3 1/2

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