Space and awareness.

It is said that the difference between buddhas and sentient beings is like the difference between the narrowness and the openness of space. Sentient beings are like the space held within a tightly closed fist, while buddhas are fully open, all-encompassing. Basic space and awareness are innately all-encompassing. Basic space is the absence of mental constructs, while awareness is the 'knowing' of this absence of constructs, recognizing the complete emptiness of mind essence. Space and awareness are inherently indivisible.

 ~ Tulku Urgyen Rinpoche

Mind is empty

Mind is empty, and while being empty, it still knows or experiences. Space is empty and does not know anything. That is the difference between space and mind. Mind is similar to space in that it is insub­stantial, not material. Isn’t it quite amazing that some­thing that is insubstantial is also able to experience?

There is mind, but it is not tangible or substantial. You cannot say that there is no mind because it is the basis of everything; it is that which experiences every possible thing. You cannot say really that there is a thing called mind, and yet at the same time you can­not say that there is no mind. It lies beyond both extremes of being and not being. That is why it is said, "Not existent, since even a buddha does not see it; not nonexistent, since it is the basis of both samsara and nirvana."

~ Tulku Urgyen Rinpoche

Buddha nature cannot be fabricated.

If our nature wasn't already enlightened, we couldn't awaken to it no matter how hard we tried. Buddha nature cannot be fabricated. Our nature is primordially enlightened, but at present our ordinary body, speech and discursive thinking obscures it. The nature of our mind, buddha nature, is like space itself, but it is space obscured by clouds. The whole point of Dharma practice is to remove the clouds and allow the actualization of what already is – the awakened state of mind, the buddha nature. The nature of our mind is primordially pure, primordially enlightened. The way to remove our two obscurations is to train in conditioned virtue and the unconditioned training in original wakefulness – the two accumulations.

~ Tulku Urgyen Rinpoche - "As It Is, Vol. 2"