Manner-of-motion verbs show both unergative and unaccusative behavior, namely the variable behavior. The variable behavior of these verbs is a problem for Perlmutter's (1978) Unaccusative Hypothesis, which claims that the unergativity or unaccusativity of a verb is based on the meaning of the verb. The Unaccusative Hypothesis loses its predictive power if a certain verb can be both unergative and unaccusative. Mateu (2005) argues that the unaccusativity of manner-of-motion verbs, which are basically unergative, is derived by their conflation into a phonologically null verb heading the canonical unaccusative structure, which is associated to the directed motion event. Despite its apparent simpler manner of explanation, this paper argues that Mateu's (2005) l-syntactic approach to the variable behavior of manner-of-motion verbs is problematic in that it induces the overgeneration problem by exploiting the overly powerful operation of generalized transformation. Although his analysis may give a correct syntactic description of the problem of the variable behavior of manner-of-motion verbs, it cannot gain the status of syntactic explanation without an additional constrained grammatical device to distinguish grammatical structures from ungrammatical configurations, such as Hale and Keyser's (2005) revision of conflation in terms of selection.

Ⅰ. INTRODUCTION
Ⅱ. PRELIMINARIES
Ⅲ. MATEU'S (2005) L-SYNTACTIC APPROACH
Ⅳ. AGAINST TOO POWERFUL L-SYNTAX
Ⅴ. CONCLUDING REMARKS
REFERENCES

• Chang-Su Lee(Youngdong University)