ABSTRACT
Chomsky (1991b) proposes general principles of economy that require derivations and representations to be minimal in cost. To provide the economy principles with full empirical content, it is of course necessary to characterize precisely the notion of “cost” in a grammar. Among other things, the status of optionality, particularly the status of optional movement, has been quite unclear under the general economy approach, which “tends to eliminate the possibility of optionality in derivation” (Chomsky 1991b: 433). Under the economy approach, “choice points will be permissible only if the resulting derivations are all minimal in cost” (p. 433). It then follows that an optional rule is allowed only if its application is “costless”, the “cost” of rule application being calculated by a certain algorithm defined in the theory of grammar. However, no concrete measure of cost of rule application has been proposed in the literature, thereby rendering the algorithm almost undefined. The purpose of this article is to propose one specific measure of the cost of formal operations in a grammar in an attempt to clarify the conditions under which optional movement is allowed in natural languages.
