Dzongsar Khyentse Rinpoche mentioned this in his recent talk at University of Carlifornia, Berkeley - Buddha once said Mind is No Mind. Mind is Luminosity.
Rinpoche clarified that though this statement itself looks and sounds contradictory but it presents the essence of the Buddha Dhamma, the non-duality nature of all phenomena.
Mind is a valid relative truth and yet when we analysed deeply enough, mind is but a concept that can be deconstructed in the ultimate truth / reality.
And this is the tricky part. Once we start to talk about the ultimate truth and conceptualise it, we must remember the ultimate truth now falls under the scope of relative truth. It is now bound by the limitations of the relative reality.
That is why Buddha often taught that the path is no path and as often he spoke of enlightenment, he also mentioned in his sermons that there is no enlightenment. Samsara and nibbana cannot be separated.
However that does not mean to say that enlightenment does not exist or is not valid anymore. As long as our minds are cluttered and bound by the notion of self, we are still trapped within the boundaries of the relative reality. And so the path Buddha prescribed is still valid, making it a useful tool to help us break free, to attain liberation in this relative reality.
When the mind is luminous, only then can we experience samsara and nibbana simultaneously, realising they are both one and not separated.
