[FOM] Notations in set theory

[Akihiro Kanamori]

Herb,
  Yes, It is from Whitehead and Russell, Principia.
`V' (with little horizontal lines on top) is the for universe
and \Lambda is for the null class.
--Best wishes, Aki Kanamori

> As I understand it, the use of V for the universal class stems from
> the use of Lambda for the nullset.  So an inverted Lambda (V) names
> the complement of the nullset.
>
> Can anyone verify this, with supporting references?
>
> --Herb Enderton
>
> On Fri, 10 Oct 2008, pax0 at seznam.cz wrote:
>> Set theory has many names whose origin is not well known,
>> such as V and L for two most important classes, square and diamond
>> principles,
>> ....
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