This paper is concerned with speculation into the nature of Enlightenment and the structure of Mind from earliest Buddhism up until the Chinese ‘Consciousness-Only’ (唯識学派) shool of the seventh centur. During this period,the notion of ‘prakrti-visuddham cittam’ is considered the predominant condition for the realization of enlightenment; yet, at the same time, it is also criticized by some Buddhist schools. With the rise of the Mahayana in India, prakrti-visuddham cittam is taken as tantamount to sunyata (‘emptiness’) or tathata (‘suchness’), which act as the key to the realization of enlightenment. According to the Consciousness-Only School(唯識学派), on the other hand, enlightenment is seen as realised by means of both impressions from learning (聞熏習) and undefiled seeds as the natural outflowing of the dharmadhatu (法界). This. paper will examine whether or not the ‘Consciousness-Only’ doctrine of Mind and Enlightenment remain consistant with Buddhism's foundational conception of impermanence.