本文旨在釐清雅美社會制度，以及由此衍生出的學術觀點與爭議中的諸多疑難。文中討論將從迄今未有定論的「父系性vs.雙邊觀」爭議出發，以闡明雅美社會為何同時顯現這兩種看似對立的結構特徵。筆者主張此一爭議兼具知識論與本體論的性質。一方面，分析家們各自透過血緣或地盤所觀察到的「親屬群體」很有可能截然不同，從而發展出對於當地社會結構的兩種迥異見解。另一方面，父系性與雙邊觀並非雅美人判定血緣關係的雙重標準，而是對於雅美社會內部雙軌秩序的表達方式，其中所指涉乃是對於地產與人力／生產工具與生產力分別發揮規範作用的兩套平行法則。儘管此二者看似分屬不同領域，然而它們皆起源於家戶――雅美社會結構的基本單元，並且共同服膺於社會生產與再生的終極目標。

This article aims at explicating the social institutions of the Yami of Lanyu and re-evaluating related anthropological theories and debates of the past fifty years. My discussions begin with a somewhat old-school but unsettled debate in Yami ethnography: Is Yami society ‘patrilineal’ or ‘bilateral’? Both ethnographers and the locals agree that Yami society reveals clear ‘patrilineality’ and ‘bilateralism’ at the same time. That is, the Yami put equal stress on patrilateral and matrilateral kin ties but also show an obvious ‘patri bias’, emphasizing solidarity among agnates in particular. As a result, the usual answer to this typological question is either that Yami society is structured according to patrilineality with a complementary principle of bilateralism or just the reverse. In the last wave of this long lasting debate, Yami society was said to be a bilateral society with patrilineal inclination, which operates on the basis of the social functions of zipos (relatives), a kind of bilateral kindred. However, the existence of patrilineality had been left unexplained until today. In my opinion, the ‘patrilinealty vs. bilateralism’ debate reflects epistemological and ontological confusions lurking in Yami ethnography and kinship studies. On the one hand, the recognition of patrilineality and ‘patrilineal descent groups’ is through ‘the soil’, based on data concerning estate and land tenure, while the recognition of bilateralism and ‘kindred and kith’ is through ‘the blood’, based on observations of the collaboration among consanguineally related persons. In other words, it was the biased selection and use of ethnographic materials that resulted in the diverging development of social theories and their contradiction. The core of the debate is not, as some researchers thought, the opposition between cultural ideals and social facts. Patrilineality is not simply a descent ideology that exists in the locals’ minds, but in the practice of the inheritance of estates, a part of social institutions. Both patrilineality and bilateralism are social facts. On the other hand, patrilineality and bilateralism are not the double standard that the Yami use to recognize consanguinity. Despite the use of ‘kinship’ concepts on the surface, both are expressions of the local political, economic, and jural relations and refer to parallel regulations inside Yami society. Whereas patrilineality regulates the transfer of land, the major means of production, bilateralism regulates the use of manpower, the major productive force. Nevertheless, patrilineality and bilateralism are of one common origin rather than being two separate domains. Both come from the framing relations in asa ka vahay (household), i.e. filiation and conjugality, and serve the ultimate goal of the social production and reproduction of asa ka vahay. A key point of this understanding is the covert status of women, whose labour and property are of indisputable importance but are often underestimated by ethnographers, and even by the locals themselves. Patrilineality, in fact, is merely the outstanding half of the ‘bilineality’ in Yami society, due to the highly visible estate and its increasing scarcity. By and large, under the co-regulation of bilineality and bilateralism, the reproduction of Yami society takes the form of neverending replication of asa ka vahay, the basic unit of Yami social structure, instead of everlasting existence of corporations such as descent groups or polities.