Vijñāna, literally “understanding,” “recognition,” or “knowledge,” refers to the function of consciousness in Buddhism. It distorts a common man’s perception of the world and inflicts mental pain on him. To relieve the pain and restore a correct view, the man has to enhance his own consciousness. Generally regarded as a school of idealism, Yogācāra, literally “mind only,” argues that all worldly phenomena are actually shaped by consciousness, which can be divided into at least two parts: the seeing and the seen. Such consciousness is able to lay the foundation for cognition even before the external world exists. According to Yogācāra, there are eight types of consciousness based on objects of cognition. The six fundamental types of sensory consciousness of the eyes, the ears, the nose, the tongue, the body, and the mind respectively perceive form, sound, smell, taste, shape, and dharma. The seventh type of consciousness is kliṣṭamanovijñāna (“deluded consciousness”), and the eighth ālāyavijñāna (“storehouse consciousness”). Kliṣṭamanovijñāna performs a function of constant reflection, on which the consciousness of the mind is posited. It also persistently conceives ālāyavijñāna as the physical self. Ālayavijñāna, the repository of the seeds of karma, keeps the purity of all types of consciousness from being contaminated, even though they are in a state of contamination themselves. In order to sort out the entanglement of pollution and purity, the School of the Mahāyānasaṃgraha proposes another consciousness, amalavijñāna (immaculate consciousness), which distinguishes truth from falsehood.

Although consciousness appears in numerous forms, there are only three categories of them in terms of function: (1) consciousness of karma execution, which constitutes the essence of the eighth type of consciousness, (2) consciousness of constant reflection, which refers to the seventh type of consciousness, and (3) consciousness of object recognition and distinction, which includes the first six types of consciousness for their sensory perception. Although six types are found in the last category of consciousness, they actually perform the same function. (Collected Commentaries to the Perfection of Consciousness-only)