His thought was heavily influenced by Immanuel Kant, whose three Critiques he translated from English, possibly first,[2] into Chinese, and above all by Tiantai Buddhist philosophy.

Over the last 40 years of his life, Mou wrote histories of "Neo-Daoist," Confucian, and Buddhist philosophy (totaling six volumes) a group of constructive philosophic treatises, culminating in his 1985 work, On the Summum Bonum (Chinese: 圓善論; pinyin: yuanshan lun), in which he attempts to rectify the problems in Kant's system through a Confucian-based philosophy reworked with a set of concepts appropriated from Tiantai Buddhism.

During that time he became a follower of Xiong Shili, author of the New Treatise on Consciousness-only and soon to be the most eminent philosopher in China until supplanted by Mou himself.

After graduating in 1933, Mou moved around the country working as a secondary school teacher and a faculty member at different universities.

It attempts to use Tiantai ontological concepts as inspiration to find Confucian solution to Kant's problem of the highest good or summum bonum.

It includes a chapter with Mou's commentary on Mencius and a more complete evaluation of the place of Daoist and Buddhist philosophy for the modern Confucian.

Mou's philosophy attempts to demonstrate the limits of Kant, suggesting instead the ways in which Chinese thought may surpass Kantian morality.

[10] In his treatise Intellectual Intuition and Chinese Philosophy (zhi de zhexue yu zhongguo zhexue) 智的直覺與中國哲學 (1971), Mou not only wrote his reflection on Heidegger’s philosophy (and translated two chapters from Being and Time), but also criticized Heidegger’s fundamental ontology with his moral metaphysics.

He agrees with Heidegger's analysis of Transcendental Schematism, which indicates that the meaning of objectification presupposes a subjective horizon that enables the object to appear.

[12] Mou rejects Kant's declaration that human beings are incapable of producing any intuitive knowledge of thing-in-itself.

[13]In general, Mou holds a critical attitude towards Heidegger's fundamental ontology in his treatise Intellectual Intuition and Chinese Philosophy: Heidegger’s descriptions could let us think of a disclosure of a “true mind” (zhen xin) for instance when he speaks about “call of consciousness”(Ruf, liangxin de huhuan), feeling of guilt ( jiuze zhi gan), dread (Sorge, jiaolü), determined being (Entschlossenheit, jueduan) or nothingness (Nichtigkeit, xuwu).

[17] According to Mou, the reason why Heidegger's fundamental ontology fails to reach the realm of moral metaphysics is that Heidegger sticks to the Kantian thesis of the finitude of human being and fails to recognize the intellectual intuition (zhi de zhijue) of human beings.

[18] Mou claims that although the study of Kant's philosophy helps him understand the relation between phenomenal world and metaphysical ontology, it is his teacher Xiong Shili who makes him realize the fundamental union of the two via the intellectual intuition.

The idea of intellectual intuition is widely manifested in Confucianism, Neo-Confucianism, Daoism and Buddhism, especially in the thought of Wang Yangming, who assimilates moral learning with the course of action such as archery and calligraphy.

According to Mou, intellectual intuition is not the central concept of a highly complex speculative system, but a form of knowledge acquired through our deeds (including emotions and intentions).

This failure limits Mou's understanding of Heidegger's philosophy only as the immanent metaphysics that stick to the attached (phenomenal) ontology.

Moral metaphysical systems have been proposed prior to Mou, most notably in the Platonic Form of the Good and the Confucian concept of dao.

This belief, that the infinite within benti similarly exists within human beings, known as the doctrine of infinite mind, can be compared with Heidegger's acceptance of being-with-others as a feature of Dasein, Wittgenstein’s rejection of a private language, and Husserl’s discussion of the immediacy of our recognition of others and their mental states within the lived world.

[5] Subsequently, Mou uses 良知 (liangzhi, or good consciousness) and 智的直觉 (zhi de zhijue, or intellectual intuition) to identify the substance in his system.

This idea reflects the human nature proposed by Mencius through the example of the apparent, innate reaction of an individual to seeing a child sitting precariously on a well (The Four Beginnings).

Mou notes that the basic implications of this example – an individual's inherent benevolence – are consistent with the autonomy of a moral subject.

[7] This autonomy, the motivating force for morality according to Mou, exists within the transcendental and philosophical mind of the individual.

[7] In accord with his notions of intellectual intuition, Mou is committed to the idea of moral transformation, whereby all individuals can transcend themselves to ultimately become sages.

In Phenomena and Noumena Mou Zongsan writes that, “if it is true that human beings cannot have intellectual intuition, then the whole of Chinese philosophy must collapse completely”.

[5] Despite the fact that this is Mou's claim, many scholars debate its validity, maintaining the legitimacy of Chinese philosophy and New Confucianism independent of intellectual intuition.

Some traditional Confucians reject Mou, citing his wholesale acceptance of Western liberty and democracy as problematic.