Abstract
1. Introduction
2. Previous Proposals
2.1. Bloom (1990)
2.2. Hyams and Wexler (1993)
2.3. The Optional Infinitive Stage
3. The Underspecification Analysis
3.1. The Backgrounds for the Underspecification Analysis
3.2. Schtze and Wexler's (1996) Assumptions
3.3. Problems with Schütze and Wexler's (1996) Assumptions
4. Revised Underspecificiation Analysis
4.1. Typology of Null Subjects
4.2. Discussion of Agr
4.3. Intrinsic Features vs. Optional Features
4.4. Revised Underspecification Analysis
5. Conclusion
References