Dalai Lama, 14th. "The Clear Light as Buddha Nature." In Mind in Comfort in Ease: The Vision of Enlightenment in the Great Perfection, translated by Matthieu Ricard, Richard Barron, and Adam Pearcey, 185–87. Boston: Wisdom Publications, 2007.
The fact that the fundamental innate mind of clear fight is the same as the buddha nature is mentioned even in the sutras, for example in The Sutra of the Wisdom of Passing Beyond, one of the root sources for Maitreya’s Sublime Continuum.
In The Wish-Fulfilling Treasury and the chapter entitled “How samsara originates from the ground,” Longchenpa discusses the ground for delusion:
The original clear light, the very essence of blissful buddhahood,
The ultimate ground of all is naturally uncompounded,
Utterly pure from the very beginning, like the sunlit sky,
Yet clouded by habitual tendencies based on ignorance,
And this is why sentient beings are deluded.[1]
In commenting upon these lines, he says:
The ground, like space, has always been free from any basis or support that depends upon samsara, and it is selfless by its very essence. It is clear and luminous like the sun or moon and spontaneously perfect. It has been present timelessly, without any beginning, and so it is beyond any transition or change.[2]
This is why the fundamental innate mind of clear light is portrayed as “uncompounded,” which, as Dodrup Jikmé Tenpé Nyima points out, means that it is continuously present and not newly created by transient causes and conditions. Longchenpa explains:
Since it is beyond all the limitations of fixed ideas, it is naturally luminous. Since it abides within the basic space in which the kayas and wisdoms are united inseparably, it is the sugatagarbha.
In other words, the full potential for the three kayas is present.
Since it supports all the phenomena of samsara and nirvana, it is called “the natural state that is the ultimate ground of all.” It is uncompounded and has always been entirely pure.
As long as we have not yet removed the adventitious stains, the fundamental innate mind of clear light is referred to as the sugatagarbha, and the potential for the three kayas that is inherently present is referred to as the qualities of basic space. When the adventitious stains that cloud our true nature are removed, the potential for these kayas, which has always been present within the fundamental innate mind of clear light, is activated or made manifest and becomes “the qualities of fruition.” Therefore the kayas and buddhahood are both intrinsic to the fundamental innate mind of clear light.