[FOM] Possible worlds

[Neil Tennant]

On Tue, 19 Dec 2006, Ignacio Nattochdag wrote:

> I quote from Lukasiewicz's paper:
> 
> "The following definition was discovered by Tarski in 1921, when he
> was attending my seminars as student of the university of Warsaw. The
> definition of Tarski is as follows:
> 
> Mp = CNpp     (This should be read : "p is possible equals if not p then p") "
> 
> The fundamental result in the paper is the following theorem:
> 
> All the traditional theorems for modal propositions are established
> free of contradiction in the trivalent propositional calculus, using
> as base the definition "Mp = CNpp".

What is the "trivalent" calculus?

In the classical calculus, this definition would render every possibilium
true.

Neil Tennant