本文旨在結合相關資料與古今研究，解析司馬遷〈報任少卿書〉的內容與作意，以闡明「司馬遷之心」。研究過程必然涉及任安來書的時間與目的、史公〈報書〉的寫作年月與真意、司馬遷行年、漢代官制，以及漢武帝晚年的政情等基本問題的考訂，最後歸結於破解〈報書〉開頭「太史公牛馬走」六字。本文首創「司馬遷之心」一詞，以有別於「司馬昭之心」。「司馬遷之心」者，就是自乞宮刑，隱忍苟活，完成《史記》，以雪恥揚親，並對自己、對父親、對歷史文化做出交代。這個意思可從「太史公牛馬走」六字的正確解讀上看出來。

This article draws upon related historical materials and research, old and new, to explicate the content and purpose of Ssu-ma Ch’ien’s letter in reply to Jen An in order to elucidate “Ssu-ma Ch’ien’s mind.” The research process for this inquiry necessarily involved embarking on a review of the following issues: 1) the time and purpose of Jen An’s original letter to Ssu-ma Ch’ien, 2) the time (month and year) and purpose of Ssu-ma Ch’ien’s letter in reply, 3) Ssu-ma Ch’ieh’s age, 4) the Han system of officials, and 5) the political situation during the latter part of Han emperor Wu’s reign. Finally, we are in a position to break through and interpret the six words with which Ssu-ma Ch’ien opened his letter: T’ai-shihkung niu-ma tsou (太史公牛馬走): Grand Historian master cow horse f1ees.This article first established the expression “Ssu-ma Ch’ien’s mind” so as to distinguish it from, say, “Ssu-ma Chao’s mind”. castration and suffering patiently despite people’s talk, so he could complete the Historical Records(Shih chi) for the purpose of washing away his disgrace and bringing honor to his father. Indeed, he made this exchange for his father and for history and culture. This essential meaning can be explicated from the six words: T'ai-shin, kung niu-ma tsou.