《春秋經》二百四十二年、魯十二公中，對於世子出生，僅有桓公六年書「九月丁卯，子同生」一條，餘皆無記錄，可見孔子之所以書，自有其特殊意涵。子同即桓公嫡子，其後繼位之魯莊公是也。《三傳》對此條經文之解讀並不一致，《左》、《公》所說與《穀梁》解經之說法大相逕庭。《左傳》詳述舉太子之禮以示桓公對子同出生之重視，《公羊》謂喜國有正故書之，義與《左傳》相近；《穀梁》則根據魯桓公夫人文姜之亂事件，認為係因當時盛傳太子同非桓公親生，而是齊襄公與文姜之私生子，故孔子書此以釋時人之疑。
本論文以《左傳》、《公羊傳》、《穀梁傳》、《詩經》、《史記》及相關典籍中有關文姜、齊襄、魯桓、魯莊間之交絡關係進行研究分析，發現當孔子著《春秋經》至此「文姜之亂」時，感時人對莊公身世質疑甚深，為別嫌明微，釋時人之疑，故特於《經》桓六年書「子同生」，以示莊公身份之正統性。因此，三《傳》說法中，以《穀梁傳》：「疑，故志之。」之解經說法為是。 There are 242 years In Spring and Autumn History. Crown princes were born without any recording, except Lu Huan Gong 6 (B.C. 706) recorded “Crown prince Tong was born in September”. Why Confucius wrote this event? It should have special meaning. Crown prince Tong was the eldest son of Lu Huan Gong. He succeeded to the throne and became Lu Zhuang Gong while grew up. This matter stated and explained in Three Biography was not identical. In this paper, we analyze the truth in Three Biography base on classical history books and present the exact meaning from Confucius.
