The existence postulate and non-regular systems of modal logic.
Anjan Shukla · Notre Dame Journal of Formal Logic · 1972
The reader is advised to read section 6 [8, pp.178-198] before proceeding with this paper, and have the book in hand.If we refer to a certain page number without indicating its source it always refers to [8].In this paper we shall use such terms as existence, proposition, etc. rather loosely.This is done on purpose to establish the continuity between Lewis's motivations and these investigations.In future we expect to give precise definitions of these terms and present further results about the systems described here.See also [6, pp.290-292].What follows has a close connection with certain remarks made there although those remarks are made in terms of models and "worlds".