This book inspires us in analyzing assertiveness of arguments in a debate setting. By using Haiidayan"s mood and modality analysis, this book reveals the argument in debating, which is the heart of critical thinking, is represented through the extensive use of the declarative mood, median probability, extension conjunctions, questions and commands in declarative, explicitly subjective modality, and the realization of metaphorical explicit subjective modality. In addition, the level of assertiveness is measured through the total number of declarative mood, conjunctive adjunct, high value of modality, explicit subjective modality, and explicit subjective modality metaphor. The study also found that the level of assertiveness relatively depends on how the students deliver their arguments. Therefore, the students might need a variety of ways in order to make their argument sound more assertive. It is evident that mood and modality analysis is helpful to understand the interpersonal meaning of debating from a new perspective, which elaborates the subtleties of language use in debating and helps us have a better understanding of it.