From Aristotle to Wittgenstein, it is a period of the Classical Theory of Category from which the Prototype Theory develops. During this period, category is regarded as a group consisting of factors with common features. In other words, category can be defined by a cluster of features or a set of necessary and sufficient conditions. According to this theory, the feature is not graded and the boundary of category is clear cut. What’s more, there is no core or margin in a category and different members enjoy the same status.  “有”的用法及其英译研究(3):http://www.youerw.com/yingyu/lunwen_11013.html