Let us first review the main theme of the sūtra itself: The three vehicles do not exist; in reality there is only One Vehicle, meaning that “there is only one form of Buddhism.” Hurvitz nonetheless draws out two component points. One is that “there is only one Path to salvation, not three.” The other is that “the Buddha is not to be delimited in time or space, or indeed in any finite terms.” The first point portrays the three vehicles as a device to attract beings to Buddhist practice. In the sūtra, this first theme is dominant and has more significance, being illustrated by four parables (Chapters 3, 4, 7, 8). The second theme is confined to only two chapters (16 and 17; in the [Tao-sheng’s commentary], 15 and 16) and is supported by one parable (Chapter 16)

In the [Tao-sheng’s commentary], no theme is more pronounced than the three-One relationship. It is certainly the central leitmotif of the text. This is evident from the start. Every component of the title of the sūtra is explained by Tao-sheng in terms of the proposition that the three unreal vehicles eventually give way to the real One Vehicle. Three of his four Dharma wheels are based on this idea.

How this theme is immersed in the individual chapters can be seen in the first paragraph of each chapter, which serves as its synopsis. Even earlier, however, we find in the beginning of Tao-sheng’s introductory chapter a tripartite breakdown of the sūtra according to this theme of three vehicles. In his analysis, the first thirteen chapters of the sūtra show that the cause of the three vehicles is really the cause of the One. The next eight chapters indicate that the effect of the three is to be identified with the effect of the One. The remaining six chapters are concerned with believers of the three in the process of becoming adherents of the One.

Tao-sheng’s connection with the T’ien-t’ai School can be viewed in terms of, among others, the two scriptures, the Nirvāṇa Sūtra and the Lotus Sūtra. It may be suggested that the importance placed on them by Tao-sheng prior to any other masters was faithfully relayed to the T’ien-t’ai tradition. The two scriptures are lumped together in the T’ien-t’ai schema of classification of teachings (p’an-chiao): in the category of the Five Periods the Nirvāṇa and the Lotus belong to the ‘final’ period. There is a subtle distinction between the two, of course: for the T’ien-t’ai School, the Lotus represents the ultimate (“round”) doctrine of the Buddha’s teaching career; whereas the Nirvāṇa, taught simultaneously, represents a résumé of all other teachings expounded before, thereby taking a somewhat penultimate position, supplementary and subsidiary to the Lotus.

In addition to his exegesis of the scriptures, Tao-sheng contributed to the development of the T’ien-t’ai School in two other ways. First, he is credited with the invention of one of the two earliest prototypes of the p’an-chiao system itself. In the [Commentary on the Lotus Sūtra], Tao-sheng puts forward a scheme of four Dharma wheels, representing the Buddha’s teaching career: the good-and-pure, the expedient, the true, and the residueless. Although Tao-sheng does not explicitly match any of the sūtras with these stages, the last two seem to suggest the Lotus and the Nirvāṇa, in that order. Being the case, this is in contrast with the p’an chiao system of the T’ien-t’ai, in which, as said before, the two sūtras are both classified as of the final period, with the Lotus accorded the more significant role. Yet, the T’ien-t’ai schema, along with a similar schema in the Hua-yen school, represents an upshot of the development started by Tao-sheng.

The second way Tao-sheng contributed to the development of
T’ien-t’ai has to do with its Eight Doctrines, consisting of one set of four “transforming methods” and a set of four doctrines. The first two, gradual and sudden teachings, probably had their origin in Tao-sheng’s theory of enlightenment, as did the later tendency to view the problem of sudden versus gradual syncretically, whereby the two were accommodated without contradiction. The germ of this perspective can be seen even in Tao-sheng and his gradualist opponent and contemporary, Hui-kuan. Gradualism can be found throughout Tao-sheng’s commentary—his division of the Buddha’s teachings itself implies nothing less than a gradual learning process. Similarly, behind Hui-kuan’s theory is a clear tolerance toward Tao-sheng’s theory. Hui-kuan in fact came up with a p’an-chiao scheme a little closer to the T’ien-t’ai and Hua-yen models than Tao-sheng’s. The two main branches of Hui-kuan’s scheme are “gradual teaching” and “sudden teaching.” Sudden refers to the Huayen Sūtra whereas gradual encompasses other sūtras and doctrines, including the Nirvāṇa and Lotus.

There are still other points of connection. For example, Tao-sheng speaks of “to converge and return” (hui-kuei) with implicit reference to the theme of the Lotus Sūtra that the three vehicles as provisional devices give way to the One Vehicle as the true goal. Tao-sheng interprets this as a dialectical process, with an overtone of “returning,” a notion harking back to the Taoist idea of “returning to the origin” (fan-pen). In T’ien-t’ai, it is paraphrased as “the three being converged to return to the One” (or “unity of three in One”) (hui-san kuei-i). The description of the “three” as “provisional” (ch’ūan) and the “One” as real (shih), encapsulated in the T’ien-t’ai phrase, “to lay the exigency [of three] open and manifest the real” (k’ai-ch’ūan hsien-shih) was originally coined by Tao-sheng. Tao-sheng is cited frequently by Chih-i (538-597), the actual systematizer of the school, throughout his various commentaries on the Lotus.

In the midst of continuing interest among clergy and nobility in Tao-sheng’s doctrine of sudden enlightenment, Tao-sheng’s thought was re-embodied in the lay scholar Liu-ch’iu (436-495). Although chronologically far removed from Tao-sheng, Liu-ch’iu’s works were remarkably similar in subject matter and methodology to Tao-sheng’s. He “expounded the meaning of [the premises] that good does not entail reward and that one achieves Buddhahood through sudden enlightenment, wrote commentaries to the Saddharmapuṇḍarika and others, and lectured on the Nirvāṇa, the large and small (Prajñāpāramitā) Sūtras, and so on,” all of which are now lost. He discussed the issue of enlightenment from the subitist perspective in his preface to the Wu-liang i Ching (“The Sūtra of Immeasurable Meaning”). The Sūtra itself is a peculiar product, believed to be a counterfeit made during the Liu Sung period (420-479), influenced by both the Lotus Sūtra and Tao-sheng’s theory of enlightenment. (The reason for its connection with the latter is that its theme is the fast attainment of Buddhahood). Here we see yet another mark of Tao-sheng’s impact throughout the fifth century. Tao-sheng’s influence may be detected not only in individual thinkers but also in several schools.

li symbolizes the object of enlightenment, constituting “truth” and what is real. Truth requires empirical verification and investigation of the real. As Tao-sheng puts it, “li should be verified and realized. This is thus called ‘truth.’ ‘Truth’ denotes investigating what is real. Hence it is called real.” This again is illustrated in a quotation of Tao-sheng by Chūn-cheng (of T’ang):

The Dharma-Master Chu Tao-sheng says: Things are necessarily caused and conditioned, without self-nature (svabhāva). Hence they are not existent. They arise in accordance with cause and conditions. Hence they are not nonexistent. Being not existent and not nonexistent both show the Dharma to be real. Being real, it is referred to as “true” (or supreme). No error, hence it is called “truth.” Contradicting what is “true,” it is called “conventional.” Not “true,” hence it is not “truth.” Therefore what is unreal and what is real are relative to each other, and the designations of “true (supreme)” and “conventional” [truths] are produced.

Here, Tao-sheng seems to suggest that the conventional as such does not constitute “truth,” but the latter is qualified by the former to compose conventional truth as one term; whereas in the case of the real (or supreme) truth, the two words match naturally with each other in their true senses.

The supremacy of the absolute domain over the relative, nonetheless, does not abrogate the value of worldly truth for the enlightened. That is so, not only because li as the symbol of the final reality unites the two domains, but also because it represents an expedient means for helping unenlightened beings. As Sangharakshita aptly puts it, “only by means of the conventional truth could the absolute truth be realized; the one was the stepping-stone to the other.” As cited previously, Taosheng clarifies: “Mahāyānistic enlightenment consists originally in not discarding what is near, the realm of birth-and-death (saṃsāra), to seek it in the far.” That nirvāṇa is not to be sought apart from saṃsāra is a Mahāyāna principle: the Mādhyamika Buddhists arrive at identification of the two by way of the principle of “emptiness.” In light of this and the fact that Tao-sheng does not depart from the Nirvāṇa Sūtra in this, it may be concluded that, as far as the notion of two truths is concerned, Tao-sheng remains a Mahāyānist, though the metaphysical structure behind the argument is shared, and probably reinforced, by neo-Taoist philosophy.

Taoism treats language as a tool somewhat deficient in unfolding ultimate reality to the full extent, as epitomized by the adage in the Lao-tzu: “Those who know do not speak; those who speak do not know” (Chapter 56). Also the Hsi-tz’u ch’uan (“Commentary on the Appended Judgements” of the I Ching), which is a text of Wang Pi’s commentary, quotes Confucius as stating: “Writing does not do full justice to words, which in turn do not do full justice to ideas” (11-12). The ineptness of words can be seen in the ineffable nature of li. Kuo Hsiang echoes this point: “The ultimate li is not something to be spoken of … li is not that which can be verbalized.”

Tao-sheng is in agreement with the Taoists on the limits of language. Various adjectival modifiers descriptive of li, such as deep, profound, wide, mysterious, far-off, and dark, all clearly identifiable in the Taoist literature, express the unspeakable nature of li. At best the role of language is to circumscribe li through approximation. He pointedly declares: “li is transcendent of words.”

Implicit in the limitation of words, on the other hand, is their intermediary value. Language belongs to the category of exigency (ch’ūan) or expediency (fang-pien, upāya). Tao-sheng declares: “li by nature is unspeakable, and yet we speak of it by resort to words in their temporary and false role, which we call expedient means.” Words as a medium or “ferry” are indispensable, especially to those who have not “witnessed” li in the course of their self-realization. In this respect, language can be best described as a catalyst in the realization of li. In Buddhist terms, it can be counted among the supporting causes (pratyaya), whereas the primary cause (hetu) making realization possible lies in the original capacity innate in human nature. …

Nevertheless, language, especially in connection with the Sage, is sometimes credited with more than a catalytic role. Here, Tao-sheng also finds common ground with the neo-Taoists. The words of the Sage, who has had an experiential encounter with li, are an authentic testimonial, a right source of mystical knowledge. Language here does not remain merely descriptive but becomes prescriptive. Therefore, in the adulation of the sūtra, repeatedly urged by the sūtra itself, there may not be anything unacceptable to Tao-sheng, whose approach in the commentary otherwise reflects a rationalist frame of mind.