The Frege-Geach Problem and the Logic of Higher-Order Attitudes.

Moral expressivism suggests that 1) moral sentences lack truth conditions and 2) our purpose in asserting moral sentences is to express non-cognitive attitudes such as desires, approval, or disapproval. Moral expressivism meets a fundamental challenge, known as the Frege-Geach problem. Sentences that express moral judgments can form part of semantically complex sentences. "P" (a moral sentence) contradicts "~P", and "Q" follows logically, by modus ponens, from (1) "P" and (2) "if P, then Q". Geach argued that noncognitivists are committed to denying that moral predicates mean the same thing in embedded contexts as they do in unembedded sentences (atomic sentences). If "P" does not mean the same as the antecedent of (2), the argument would be invalid. The problem is that the above-mentioned argument is obviously valid. Blackburn has argued that the complex sentence expresses a 'higher-order' attitude toward the attitudes expressed by the smaller sentences which make it up. If we accept the premises of a valid argument but deny its conclusion our attitudes clash in the same way that they do if we both believe that P and ~P. Blackburn's metaattitudes approach faces several problems. Someone who endorses the premises but denies the conclusion of the valid argument commits himself to a moral inconsistency, not a logical one. In addition, uttering both 'P' and '~P' seem to be inconsistent but expressivism cannot explain the inconsistency between these two obviously inconsistent sentences. Blackburn's strategy of inventing a new attitude, such as tolerance, is also unable to solve this problem. [ABSTRACT FROM AUTHOR]