Although Tsongkhapa did not author a commentary on the Ultimate Continuum, his main student and successor at his main seat of Ganden, Gyaltsap Je Darma Rinchen, composed an elaborate commentary on the Ultimate Continuum. The commentary, filling 230 folios, was composed at Nenying temple at the request of Gungru Gyaltsen Zangpo and others after Gyaltsap had received teachings on it from both Rendawa and Tsongkha. One Tagtsel Kharkhap Dhondup Kunga served as the scribe for this voluminous and meticulous commentary, in which Gyaltsap carries out a relentless critique of the theory that buddha-nature is inherently endowed with qualities of the Buddha or that it is an absolute eternal reality empty only of other adventitious conventional phenomena.
A good example of such critique is Gyaltsap's reductionist refutation of the interpretation of Verses I.24-25 found in earlier commentaries, which generally follow Asaṅga's commentary. Verses I.24-25 state (translation by from Karl Brunnhölzl's When the Clouds Part):
- The disposition of the three jewels
Is the object of those who see everything.
It is fourfold and is inconceivable
For four reasons in due order.
- Since it is pure and yet associated with afflictions,
Since it is not afflicted and yet becomes pure,
Since its qualities are inseparable,
And since [its activity] is effortless and nonconceptual.
The verses, following the Śrīmālādevīsūtra, point out that buddha-nature is inconceivable in four different ways: (1) it is pure and yet with defilements, (2) it is never defiled and yet becomes pure later, (3) it has all the qualities of the Buddha while remaining in the defiled sentient beings, and (4) it is without conceptual thought and yet can achieve spontaneous activities. To further illustrate this paradoxical and inconceivable state of the buddha-nature, particularly the third point, Asaṅga cites the analogy of the cosmic painting from the Buddhāvataṃsakasūtra (translation from Karl Brunnhölzl's When the Clouds Part):
- O son of the victor, it is as follows. Suppose there were a big canvas the size of the worldly realm that is the biggest chiliocosm in a trichiliocosm. On this big canvas the entire worldly realm that is the biggest chiliocosm in a trichiliocosm would be painted in its complete form. That is, the great ring of iron mountains would be painted in the size of the great ring of iron mountains. The great [golden] ground would be painted in the size of the great [golden] ground. The worldly realm of a dichiliocosm would be painted in the size of the worldly realm of a dichiliocosm, the worldly realm of a chiliocosm in the size of the worldly realm of a chiliocosm, the four-continent [worlds] in the size of the four-continent [world], the great oceans in the size of the great ocean, the continents of Jambū in the size of the continent Jambū, the continents of Pūrvavideha in the size of the continent Pūrvavideha, the continents of Godāvarī in the size of the continent Godāvarī, the continents of Uttarakuru in the size of the continent Uttarakuru, the [Mount] Sumerus in the size of Sumeru, the palaces of the gods living on the earth in the size of the palaces of the gods living on the earth, the palaces of the gods living in the desire [realm] in the size of the palaces of the gods living in the desire [realm], and the palaces of the gods living in the form [realm] in the size of the palaces of the gods living in the form [realm]. [Thus,] this big canvas would have the size of the vast expanse of the worldly realm that is the biggest chiliocosm in a trichiliocosm. Then, this big canvas would be inserted into a single particle [the size] of the minutest particle. Likewise, just as this big canvas would be inserted into a single particle [the size] of the minutest particle, big canvases of that same size would be inserted inside all particles [the size] of the minutest particle without exception.
- Then, there would appear some learned person, clever, intelligent, wise, and endowed with the profound investigative skill pertinent to [these canvases] here. His divine eye would be perfectly pure and lucid. With that divine eye, he would look [and think], "This big canvas of such a nature stays here in such a limited single particle [the size] of the minutest particle. It does not sustain any sentient being." So he would think, "Breaking apart this particle [the size] of the minutest particle with the strength and power of great vigor, I shall make this big canvas into what sustains the whole world." Giving rise to the strength and power of great vigor, he would break apart that particle [the size] of the minutest particle with a tiny vajra and, according to his intention, make that big canvas into what sustains the whole world. Just as for one, he would do the same for all minutest particles without exception.
- Likewise, O son of the victor, tathāgata wisdom, the immeasurable wisdom that is the wisdom that sustains all sentient beings, pervades the mind streams of all sentient beings in its entirety. All these mind streams of sentient beings are also as immeasurable as tathāgata wisdom. Nevertheless, naive beings, who are bound by discriminating clinging, do not know, cognize, realize, and perceive this tathāgata wisdom. Therefore, the Tathāgata, after having seen the states of all sentient beings [whose nature is the] dharmadhātu with unobstructed tathāgata wisdom, resolves to be a teacher. [He thinks,] "What a pity! These sentient beings do not realize tathāgata wisdom, just as it is, [though] they are pervaded by this tathāgata wisdom. Through teaching them the noble path, I shall remove all the fetters of these sentient beings that they create through discrimination so that they, by themselves, undo the big knot of discrimination through adopting the power of that noble path and then recognize that tathāgata wisdom [in themselves] and attain equality with the Tathāgata." [Accordingly,] through the teaching of the path of the Tathāgata, they remove all fetters created by discrimination. In those in whom all fetters created by discrimination have been removed, this immeasurable tathāgata wisdom becomes what sustains the entire world. (353–55)
Gyaltsap, who wrote commentaries on both the root verses and on Asaṅga's commentary, takes a very logical and reductionist approach to this presentation of inconceivability of the buddha-nature. He explains that the first reason for inconceivability refers to the difficulty in fathoming the nature of sentient beings being empty of any inherently existent entity, which makes all conventional engagements possible. The second reason, he argues, refers to the difficulty in understanding how buddha-nature is earlier never the object of defiling thoughts but later becomes free from defiling emotions. He does not agree that buddha-nature (i.e., reality) is not defiled or afflicted but interprets the verse by saying it is not an object of afflictive emotions.
Regarding the third point, he says that the impossible hypothetical analogy of the trichiliocosmic painting is given in order to dispel the misconception that would arise in ignoble followers who would hold that the qualities of the Buddha exist in sentient beings. "Other than that, what use is such an impossible analogy?" he remarks. Gyaltsap seems to suggest that the purpose of the highly exaggerated analogy is to stop people from believing that sentient beings have a buddha-nature endowed with all qualities, quite contrary to how the sūtra and Asaṅga's commentary uses the analogy to illustrate sentient beings have the immeasurable buddha qualities.
According to Gyaltsap, only the potential or possibility for the buddha qualities to arise exists in the sentient beings, and the reality, the actualization of which can lead to buddha qualities, exists in sentient beings, but not the actual qualities. If a buddha-nature or dharmakāya which is pure by nature and also pure from adventitious afflictions exists, is it permanent or impermanent, he inquires. If it is permanent, it will entail that all sentient beings are already buddhas. If one were to say that such a being who is a buddha does not realize that he/she is a buddha, it is a serious disrespect to the Buddha to even think such an ignorant being who cannot distinguish a buddha from sentient beings is a buddha.
Furthermore, Gyaltsap asks if such a buddha-nature endowed with buddha qualities is obscured by afflictive emotions or not. If it is, then it follows that it does not have the buddha qualities because a buddha is defined by the elimination of such afflictions. If it is not obscured by afflictive emotions, then it would follow that even the sentient being, in whose mind stream such pure buddha-nature exists, is also not obscured by afflictive emotions because they are of the same stream of consciousness. If such a buddha-nature is identical with the nature of the sentient being, how could the sentient being be by nature both obscured by afflictive emotions and free from them? If such a buddha-nature is a different entity from the sentient being, then one will be forced to accept the simultaneous existence of the natures of a buddha and sentient being.
Using such a dialectical reductionist approach influenced by the logic and epistemological tradition, Gyaltsap refutes the validity of the philosophical position that claims buddha-nature to be endowed with the qualities of the Buddha. To him, the term buddha-nature refers to the ultimate reality, the object of a meditative gnosis of a sublime being, which, if fully realized, leads to the attainment of Buddha's wisdom and qualities. As such a reality exists in sentient beings, it is taught that the Buddha's wisdom and qualities exist in the nature of the sentient beings.