If the meditator wishes to go further into the formless realms, then they should continue to cultivate attention to boundless space and begin to notice that they are conscious of all of it, and thus space is filled with consciousness. As some point the mind will abandon boundless space and shift to perceiving boundless consciousness, the sixth jhana. This can feel outrageously unitive, as consciousness seems to fill the whole universe. Space becomes “luminous,” and this can be confused with descriptions of the fundamental luminosity of awareness and with non-duality, though this is definitely not the attainment of the understanding of those. Again, equanimity prevails. This state has a sense of presence to it that boundless space doesn't. It is also a great staging ground for exploration of the “psychic powers.”

From here the meditator has various options. They can get stuck, which can happen fairly easily if they are mistaking dzogchen or other non-dual formless practices for meditation on the concentration object of boundless consciousness, again due to misunderstanding or overemphasizing the phrase “space-like awareness.” They can also go on to cultivate the next formless realm (nothingness), or they can investigate boundless consciousness and then begin the progress of insight.

For this last option, extremely careful attention must be given to each moment that the sensations that make up the perceptions of consciousness, vastness, or equanimity arise and pass away. Great precision must be given to the fact that these sensations do not satisfy and cannot be self or imply a separate self. Because of how fundamentally disconcerting (unsatisfactory) it can be to have the three illusions shattered at this level of clarity and simplicity, this is not an easy practice but can be very powerful. It is actually much more likely that such insights into the true nature of the three first formless realms will arise spontaneously due to previous skillful insight practices.

Again, experiencing boundless consciousness strobing in and out of reality can be profoundly helpful in convincing us that even boundless consciousness that fills the vastness of space is not awareness, though awareness cannot be said to be separate from consciousness. What is observing boundless consciousness strobe in and out of reality? Now, there is a question, perhaps The Question.

MCTB Nothingness, The Seventh Jhana