Is ethics equal to moral science? This question involves how to understand the nature and status of ethics as a discipline. It is also essential to how to "rewrite Chinese ethics". Three predecessors in ethics put forward different opinions to this question. ZHOU Yuan-bing insists that ethics is "moral science". However, ZHOU Fu-cheng and FENG Qi hesitated to accept this opinion, respectively putting forward their unique understandings on the relationship between ethics and philosophy, the construct of ethics with Chinese characteristics and other important issues. An examination of their disputation will bring inspiration for us to "rewrite Chinese ethics" today.