 Recently, there has been a lot of interest in discovering ways of repairing the Fregean theory of extensions. The traditional view is that one must either restrict Basic Law V or restrict the Comprehension Principle for Concepts. Recently, Boolos (1986, 1993) developed one of the more interesting suggestions for revising Basic Law V without abandoning second-order logic and its comprehension principle for concepts. On the other hand, there have been many suggestions for restricting the Comprehension Principle for Concepts. The most severe of these is to abandon second-order logic (and the Comprehension Principle for Concepts) altogether. Schroeder-Heister (1987) conjectured that the first-order portion of Frege’s system (i.e., the system which results by adding Basic Law V to the first-order predicate calculus) was consistent and this was proved by T. Parsons (1987) and Burgess  (1998).[4]  Heck (1996), Wehmeier (1999), Ferreira &amp; Wehmeier (2002), and Ferreira (2005) consider less drastic moves. They investigate systems of second-order logic which have been extended by Basic Law V but in which the Comprehension Principle for Concepts is restricted in some way. See also Anderson &amp; Zalta (2004) and Antonelli &amp; May (2005) for different approaches to repairing Frege’s system. See Fine (2002) for a discussion of the limits of Frege’s method and see Burgess (2005) for a good general overview.