I'd like to talk about space.
In my understanding of Dzogchen, there are three kinds of space that we can talk about. There's the ordinary, dualistic outer space in which things exist. In relation to the practice of Trekcho practice, there are two other types that are discovered. There is also the inner space of the mind where thoughts etc. are experienced as being without any kind of actual 'place' of appearing or thing that creates them. This is inner ying - nang ying (nang dbyings). The outer space has a similar nature, where there is no fixed place to things that arise and they are not solid or within any kind of objective frame of reference. Basically, there's no place they arise, stay or disappear - similar to the nature of the mind. This is outer ying - chos ying.
I've a few questions/things I'd like to discuss:
Is there anything other than a nominal difference between outer ying and inner ying? What exactly is the relation between normal space and the two yings? Is it simply ying that has been frozen by grasping?
To what extent can space said to be emptiness itself? I know that there is a danger in Dzogchen of merely meditating on space.
What is the exact relationship between inner ying, outer ying and rigpa? It's my understanding that the yings are the space-like nature of rigpa.