His philosophy attempts to create a comprehensive worldview that includes and sublimates all Buddhist and non-buddhist teachings of his time into a single harmonious spiritual vision.

In an 811 letter to Chengguan, he wrote that for three years he "gave up eating meat, examined [Buddhist] scriptures and treatises, became familiar with the virtues of meditation and sought out the acquaintance of noted monks.

[7] He propounded the necessity of scriptural studies in Chan, and was highly critical of what he saw as the antinomianism of the Hongzhou lineage derived from Mazu Daoyi (709–788), which practiced "entrusting oneself to act freely according to the nature of one's feelings".

[10] In 812 Zongmi travelled to the western capital, Chang'an, where he spent two years studying with Chengguan, who was not only the undisputed authority on Huayan, but was also highly knowledgeable in Chan, Tiantai, the vinaya and East Asian Mādhyamaka.

[11] In 816, Zongmi withdrew to the Zhongnan Mountains southwest of Chang'an and began his writing career, composing an annotated outline of the Sutra of Perfect Enlightenment, and a compilation of passages from four commentaries on the sūtra.

[13] In mid-823, he finally finished his own commentary on the text that had led to his first awakening, Sutra of Perfect Enlightenment, and the culmination of a vow he had made some fifteen years earlier.

Zongmi was summoned to the capital in 828 by Emperor Wenzong (r. 826–840) and awarded the purple robe and the honorific title "Great Worthy" (大德; dade; bhadanta).

[15] During this time, Zongmi turned his considerable knowledge and intellect towards writing for a broader audience rather than the technical exegetical works he had produced for a limited readership of Buddhist specialists.

A high official and friend of Zongmi, Li Xun, in connivance with Emperor Wenzong of Tang and his general Zheng Zhu, attempted to curb the power of the court eunuchs by killing them all.

According to Broughton, Jinul's influential Excerpts from the Separately Circulated Record of the Dharma Collection with Inserted Personal Notes "is an expression of sutra-based sudden awakening gradual practice Guifeng Chan".

[23] Through the influence of the Mind Mirror, Zongmi-Yanshou Chan also reached Japan, were it was influential on the Daruma school of Zen and on the thought of early Rinzai figures like Myoan Yosai (1141–1215) and Enni Ben'en (1202–1280).

"[37] Zongmi's lifelong work was the attempt to incorporate differing and sometimes conflicting systems into an integrated framework that harmonized various Buddhist teachings and traditions, especially those of Chan practice and Huayan doctrine.

[39] Metaphysically speaking, Zongmi moves beyond the thought of earlier Huayan thinkers like Fazang, who emphasized the doctrine of perfect interfusion or unobstructed interpenetration.

[42] Zongmi's classification system, influenced by previous Huayan schemas like those of Fazang and Chengguan, provided a schematic analysis of various teachings and practices which explained and harmonized their differences.

"[59] In the Chan Letter, Zongmi explains the mind ground through the simile of the wish fulfilling jewel (cintamani) which is like a crystal ball reflecting many colors.

[66] Zongmi cites the Avatamsaka sutra which states that "there is not a single sentient being that is not fully endowed with the wisdom of the Tathagata" as a major source for this teaching.

[68] This ultimate ground of reality, the "dharmadhatu of suchness" (chen-ju fa-chieh), is, according to Zongmi, "the pure mind that is the source of Buddhas and sentient beings.

Sudden awakening provides an initial insight into the true nature and gradual cultivation was needed to eliminate all remaining traces of defilements that prevented the total integration of the originally enlightened mind into all actions.

[98] This is the way in which the following simile by Zongmi on Chan (which is beyond words) and the scriptures is to be understood:The sutras are like an inked marking string [shengmo], serving as a model by which to establish the false and the correct.

"[103] This shows Zongmi's basic doctrinal tendency which as Gregory explains "is always to articulate a comprehensive framework in which such discrepant perspectives can be harmoniously subsumed.

[107] Zongmi criticized this on the basis that the Northern school was under the misconception that impurities were inherently different or separate from the pure mind, making this a dualistic view that fails to understand the natural working of intrinsic enlightenment.

[112] According to Zongmi, the Hongzhou teaching led some foolish people to a radical nondualism that believed that all actions, good or bad, and all experiences (anger, greed, pleasure, pain) were totally equal expressions of the Buddha-nature.

[115]Thus, while Zongmi acknowledged that the essence of Buddha-nature and its expressions in the world are non-dual, he insisted that there is still a difference between good and evil, and affirmed the need for spiritual cultivation.

Gregory writes that to avoid the dualism he saw in the Northern Line and the radical antinomianism of the Hongzhou school, Zongmi's paradigm preserved "an ethically critical duality within a larger ontological unity".

According to Zongmi, this school had misinterpreted Shenhui's teaching on "no-thought" as entailing "the rejection of all forms of traditional Buddhist ethical practice and ritual observance.

[However] if it be a matter of investigating the myriad phenomena, exhausting principle, realizing the nature, and reaching the original source, then Buddhism alone is the ultimate judgment.

[124]Zongmi's early training in Confucianism led him to attempt to develop a syncretic framework where Chinese non-Buddhist principles could be integrated within Buddhist teachings.

[127] For example, Zongmi matches the five precepts with the five Confucian virtues (benevolence, righteousness, propriety, trustworthiness, wisdom), and he links Buddhist cosmological processes with Daoist cosmogony.

[18] Zongmi also wrote a major work in eighteen fascicles called A Manual of Procedures for the Cultivation and Realization of Ritual Practice according to the Scripture of Perfect Enlightenment.

According to Gregory, the work is influenced by the writings of Zhiyi and explains a "complex program of ritual and meditation practice in terms of the Scripture of Perfect Enlightenment.