《孟子．告子上4》載告子「仁內義外」之主張曰：「仁，內也，非外也；義，外也，非內也。」孟子批判告子「義外」，對「仁內」則似乎認可，對於此點，歷來治《孟》者並無確解。由於告子的「仁」乃是出自其自然人性論，為使孟、告二人的「仁」不相等同，學者或以「情感之愛」、「屬氣」理解之。在此格局下，告子為代表的「義外」，便成為孟子「義內」思想的最佳對照組，而有「心靈窒塞」等批評。然而，告子「仁內義外」乃是宗族制度處理門內、門外社會關係「親親尊尊」的傳統思路，《禮記．喪服四制》、郭店楚簡〈六德〉皆有門內、門外之說。考諸《孟子》文本，亦見仁義對應於父子、君臣（即血緣之情與社會關係）的用法，《離婁．上27》更有「仁之實，事親是也。」之謂。易言之，血緣親情可能是孟、告子二人「仁內」的交集點。順此推論，則孟子言仁義雖已不僅於愛親，更要求放諸四海，但思想發展過程中仍不免留有宗法意義的親尊遺跡。準此，孟子言義內，但對禮制仍保有極大的尊重。儘管內在的義乃是客觀禮制的決斷者，但客觀禮制是否亦為義的根源之一？又是否需透過後天學習乃得？若然，「義」便不能說沒有「定之於外」的可能，惟終極判準仍訴諸內在之義。如果客觀禮制乃是內在良知朗現所自然流露，「義」當然絕對內在，而無「定之於外」的問題，則「義內」便不僅是終極判準，也是唯一根源。由於孟子本人對此並無進一步說明，後世朱熹、象山、陽明等人遂生歧解，更分別以此二種態度，質疑相對立場為告子、為「義外」。綜上所述，透過告子「仁內」、「義外」之對比，可析分孟子言「義」當有「宗法制度下的適用對象」、「道德判準」、「道德根源」等三種可能義蘊，此為拙文所欲論述之旨。

Gaozi's opinion that Ren(love) is inside but Yi(Justice) is external is documented in Mencius. However, Mencius only criticized that Yi is external, without comment on that Ren is inside. It seems that Mencius agrees with the latter opinion. Gaozi's humanism is based on the naturalism, so that scholars always interpreted the love as physical affection to distinguish Gaozi's Ren from Mencius'. Consequently, Gaozi's Yi external becomes the best contraction with Mencius's Yi inside.However, Gaozi's opinion that Ren(love) is inside but Yi(Justice) is external is applied to deal with relationships respectively inside and outside the family. Such statements are recorded in Liji(Book of Rites), Liude(bamboo book), and so on. Such usage is also documented in Menzi(the text of Mencius). That is to say, Ren(love) inside may be the intersection of Mencius and Gaozi. Consequently, patriarchal vestige is unavoidably reserved in the development of Mencius' thought.Besides, with the advocacy of inner Yi, Mencius still extremely values the ritual system. No doubt, inner Yi is the criterion of ritual system. However, is ritual system one source of Yi? Is ritual system acquired by postnatal learning? If so, then we cannot deny the possibility of outside Yi, but inner Yi is still the ultimate criterion. On the contrary, if Yi derives from conscience, Yi will be not only the ultimate criterion but also the only origin. Without Mencius' determinate statement, therefore, there are different interpretations by Zhuxi and Wang yanming. By the contrast of Gaozi's Yi external, we can distinguish the three meanings of Mencius's Yi.