| Acknowledgements | 第1-6页 |
| Abstract | 第6-8页 |
| 摘要 | 第8-10页 |
| Contents | 第10-12页 |
| List of Tables and Figures | 第12-13页 |
| List of Abbreviations | 第13-14页 |
| Chapter One Introduction | 第14-19页 |
| ·Background of the Study | 第14-15页 |
| ·Purposes and Significance of the Study | 第15-17页 |
| ·Data and Methodology | 第17-18页 |
| ·Organization of the Thesis | 第18-19页 |
| Chapter Two Literature Review | 第19-23页 |
| ·Previous Studies on American Presidential Debates | 第19-23页 |
| ·A Brief Introduction of American Presidential Debates | 第19-20页 |
| ·Linguistic Studies on American Presidential Debates Abroad and in China | 第20-23页 |
| Chapter Three Theoretical Basis | 第23-30页 |
| ·An Overview of the Appraisal Theory | 第23-25页 |
| ·Attitude | 第25-27页 |
| ·Engagement | 第27-28页 |
| ·Graduation | 第28-30页 |
| Chapter Four Modality System in O-R’s Televised Presidential Debates | 第30-47页 |
| ·Halliday’s Classification of Modality System | 第30-39页 |
| ·Types of Modality | 第31-35页 |
| ·Orientations of Modality | 第35-37页 |
| ·Values of Modality | 第37-39页 |
| ·The Distribution of Modality System in the Three Debates | 第39-47页 |
| Chapter Five Analysis of Modality System in O-R’s Televised Presidential Debates | 第47-78页 |
| ·The Connections Between Appraisal System and Modality System | 第47-51页 |
| ·Analysis of the Interpersonal Meaning of Modality System in the Three Debates | 第51-78页 |
| ·Modality System and Judgment | 第51-66页 |
| ·Modality System and Social Esteem | 第52-58页 |
| ·Potentiality and Capacity | 第52-56页 |
| ·Inclination and Tenacity | 第56-58页 |
| ·Modality System and Social Sanction | 第58-66页 |
| ·Probability and Veracity | 第58-63页 |
| ·Obligation and Propriety | 第63-66页 |
| ·Modality System and Heterogloss | 第66-78页 |
| ·Modality System and Dialogic Expansion | 第67-70页 |
| ·Modality System and Dialogic Contraction | 第70-78页 |
| Chapter Six Conclusion | 第78-84页 |
| ·Major Findings of the Study | 第78-81页 |
| ·Implications of the Study | 第81-82页 |
| ·Limitations of the Study and Suggestions for Further Study | 第82-84页 |
| References | 第84-88页 |
| Publications | 第88页 |
