An?tman, from the time of Buddha''s teaching, is the prominent doctrine of Buddhism, which means there is no self which we regard as real entity. Still, we falsely think of ourselves and world as enduring, substantial entities. And from this ignorance regarding self and world, we have the fundamental source of suffering in the mind. According to Buddha''s idea of compassion, Buddhist thinkers have made efforts to liberate ourselves from suffering by eliminating this ignorance, which results in our afflicted conceptualization. Based on the doctrine of the emptiness of all entities, on which Mah?y?na Buddhism puts its emphasis, Yog?c?ra school explores the problems of consciousness and world to eliminate the ignorance, asserting that the world is not different from the consciousness that perceives it and so purified consciousness can liberate people from suffering in the world. Hence Vasubandhu argues that when the consciousness is purified by the transformation of basis, defiled mentation, distorting our understanding, disappears and the world is seen as it is with the mind of a buddha.
The Ch''eng wei-shih lun(成唯識論) is said that Xuanzang(玄?) compiled and translated ten distinct Sanskrit commentaries of the Thirty Verses on the Vijnapti-matra Treatise(唯識三十頌) written by Vasubandu into its Chinese commentary in 659. The Ch''eng wei-shih lun aims to explain the principles about emptiness of self and dharmas(我空, 法空) to eliminate two obstacles, afflictive hindrance(煩惱障) and cognitive hindrance(所知障), respectively resulting from the attachments of self and dharmas(我執, 法執), which hinder liberation and enlightenment. The Ch''eng wei-shih lun argues that the basis of the attachment are the sixth consciousness(意識) and manas(末那識), and especially continuous and inherent(俱生) attachments are based on manas. So the purpose of this dissertation is to explore the manas in the Ch''eng wei-shih lun; concretely it is to examine the definition of manas and the proof of its existence, find out its natures and functions, and illuminate them in the perspectives of practices for liberation and enlightenment.

First, manas in the Ch''eng wei-shih lun is defined as the consciousness which exists continuously before and after transformation of basis(轉依: ??raya-par?v?tti), and has the nature of thinking and measuring constantly and subtely. The Ch''eng wei-shih lun demonstrates the existence of manas in the eighth aspect. It used two modes of its demonstration; the first mode is proving by the evidences on holy teachings(聖敎證), the second mode by those on scriptures and reasoning(正理證). By the first mode, the first and the second of manas'' eightfold aspect are acceptable as the truth, because of the consistency to holy teachings. Also, among the other six proofs by the second mode, the first, the second, and the sixth are acceptable on account of the consistency of their reasoning. Especially the fist is correspondent with everyday''s experience, as well as with the scripture.

Second, there are two types of conditions for manas to act; one is a support(所依) and the other is an object(所緣). The supports of manas are three types, seed-basis, shared basis, and initiating and guiding support, which are respectively, in Early Buddhist schools. The first type of supports is seed-basis(種子依). From the ground that the naming of seed is valid on both no-defilement(無漏) and defilement(有漏), the designation of the first support, seed-basis, clearly shows the arguing points of the Ch''eng wei-shih lun that manas, the seventh consciousness, functions as defiled mentation(染汚末那) before the transformation of basis, and still continue to constantly be acting as purified mentation(淸淨末那) after the transformation.
The second type of supports is the shared basis(俱有依). According to the Ch''eng wei-shih lun, the seventh consciousness, manas, has only one shared basis, the eighth one, ?layavijn?na, which has the seventh one as only one shared basis, too. So manas and ?layavijn?na always become each other''s only one shared basis at the same time. Given this way of their relation as shared basis, like Ch''eng wei-shih lun is arguing, if the eighth consciousness remains after basic transformation, it would accompany the seventh consciousness as shared basis, and thereby manas would remain after the transformation. Also, in the reverse order, it leads to the same result that if the seventh consciousness is sure to remain after basic transformation, the eighth one would be accompanied with it, so there would be the eight one.
The initiating and leading support(開導依), as the third type of supports, is described in the Ch''eng wei-shih lun to adopt the same kind of consciousness as its supports, and thereby that of manas should become the seventh consciousness except mental functions(心所) previous to one moment.
Along with these supports, the other condition is the object of manas. In the Ch''eng wei-shih lun, manas has the subjective part(見分) of the eighth consciousness as its object before transformation of basis, and suchness(眞如: tathat?) or all dharmas(諸法) are the object of manas after the transformation.

Third, manas is the foundation of posting a self(我執) and attaching to dharmas(法執) before the transformation of basis, but it becomes the foundation of Equalization Cognition(平等性智) after basic transformation. On this assumption of manas, the Ch''eng wei-shih lun makes the nature and functions of manas clear in the course of practicing the path of enlightenment.

In the Ch''eng wei-shih lun, the practicing stage falls into two divisions by the transformation of basis. Before the transformation, the stages are divided into two part; the first stage has the attachment of both self and dharmas in the mind, but the second has the only attachment of dharmas. After achieving the transformation, the mind becomes the Final Status(究竟位). Before the transformation, the nature of manas, which still has attachments, takes on an obstruction(有覆) and moral indeterminacy in karma(無記), because of its subtle activities. Also manas go with the mental functions, which are four primary afflictions(根本煩惱), five omnipresent mental functions(遍行心所), eight everywhere- defiled afflictions(遍染隨煩惱), and the wisdom mental factor(慧心所) as one of object-contingent mental factors(別境心所). After achieving the basic transformation, the nature of manas gets the quality of goodness, and its mental functions have five omnipresent mental functions, five object-contingent mental factors, and all of eleven good mental factors(善心所).
The doctrine of consciousness-only, on the ground of Buddha''s compassion, has put their fundamental aims in explaining the natures and causes of suffering and teaching the way to liberate self and others from suffering. As Schmithausen indicated, though Xuanzang knows that suchness(tathat?) can not be explained by means of language, on this base he elaborates system of the eight consciousness in the Ch''eng wei-shih lun, for the purpose of explaining the principle of suchness by indirect way, namely, by language. Just as did Buddha at his time, so Xuanzang tried to give common people such convincing explanations that they could listen to reason and accept in their own standpoint, so that they lead to the realization to liberate themselves from suffering. By this dissertation, it has been found out that on the ground of compassion, the Ch''eng wei-shih lun is the doctrine accepting common people as they are, and giving the hope that they can become Buddha''s mind, in that manas, thinking and measuring consciousness, which takes leadings roles in everyday''s experiences, exists constantly before and after the transformation of basis, namely liberation.