FOM: Cardinality Operators
Martin Davis
martin at eipye.com
Thu Jan 27 13:48:09 EST 2000
At 09:27 AM 1/27/00 -0500, Harvey Friedman wrote:
>Digression: Is NBG or VB more historically accurate as a name for this
>class theory? I.e., what exactly was Godel's role?
His monograph on the consistency of GCH used a modification of Bernays'
modification of von Neumann's axiomatization. The progression was like
this: Von Neumann had two sorts, sets and mappings; Bernays replaced the
mappings with classes but retained separate sorts; Goedel merged the two
sorts defining a set as a member of a class. He took over Bernays' proof of
comprehension for classes from a finite set of axioms, and of course his
monograph popularized the system.
Martin
Martin Davis
Visiting Scholar UC Berkeley
Professor Emeritus, NYU
martin at eipye.com
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