Harvey M. Friedman
Ohio State University
September 29, 2005
1. INFORMAL INTROUDCTION TO PROOFLESS TEXT.
We give an informal account of some of the essential
features of proofless text.
i. Proofless text is based on a variant of ZFC with free
logic. Here variables always denote, but not all terms
denote. If a term denotes, then all subterms must denote.
The sets are all in the usual extensional cumulative
hierarchy of sets. There are no urelements.
ii. Every set, in addition to having elements, plays some
additional roles. It acts, for each n 1, as an n-ary
relation. It also acts, for each n 1, as an n-ary
function. As an n-ary relation, it may fail at any n
arguments. As an n-ary function, it may be undefined at any
n arguments. We use s(t1,...,tn) and s[t1,...,tn] for this