
 Syntactic and Semantic Foundations of Predicate Logic 
  Whereas, semantically, a 2place predicate says something about a relationship between two elements of a set, a 0place predicate just ``says something'' (which may be true or false, in a given state), but says nothing about the elements of the set in question. 
  In propositional logic, one has the ``standard models'' for interpreting the uninterpreted strings of symbols that we recursively defined as sentences (we have the notion of truth value assignments, of states, of the truth table definitions of the connectives, etc.). 
  One can go further and introduce ``predicate logic with equality and function symbols'', ``typed predicate logic'', ``theories'', in which certain predicate symbols and function symbols are singled out for special roles in supplemental axioms of the logic, etc. We may not have time for much beyond pure predicate logic. 
 www.math.yorku.ca /Courses/9798/Math2090/predsyntax/predsyntax.html (518 words) 
