  Sadly, Gregory Fitch passed away January 27, 2007.  Prior to his death, he made arrangements for Michael Nelson to take over the entry as co-author.  Although the two authors discussed much of this material and shared a common perspective on the content of this article, Sections 3 and especially 4 are new and were written independently by the new co-author. Fitch's original, solely authored entry is available in the SEP Archives, at   &lt;https://plato.stanford.edu/archives/sum2005/entries/propositions-singular/&gt;.  (See the version history.)  Thanks to Penelope Mackie for extremely helpful editorial advice.