From a non-dual perspective, the essence of mind is calm concentration; movement of mind is phenomenal emergence at the 6 sense doors. Essence and movement are the same thing: like energy and matter, the ocean and its waves, the sun and it’s rays, or a movie screen and the sounds/images projected on it. Seeing them as separate cultivates the duality of clinging and rejection.
To “meditate” simply means to maintain presence of both the calm state and movement of mind (recognition and continuation of pure, non-dual presence): there is nothing to “meditate on”. Any thoughts, sensations, desires, etc should be simply allowed to self-liberate at the very instant of their arising through a presence imbued with awareness – these conditioned phenomena are all apertures leading into the Ground of Still and Silent Presence; of Primordial Core-Awareness.
“Truth is one, many is its names” (Rig Veda). “Non-dual” is the inseparability of the Relative appearance (Particular) and the Absolute emptiness (Universal) [Christ-YHWH; and Practice/Realization/Awakening is (the action and result of) Spirit]
The process of conceptual cognition categorizes sensory cognition and all of mental cognition (which includes conceptual cognition) as “this”s and “that”s: mental objects that represent, are derived from, and resemble (or construct?) external (material) perception and that filter internal (mental) perception – this is the root cause of duality: physical and mental things we “know” are the causes and the ways we know them are the effects; direct experience and our conceptions of experience are distanced and bifurcated in time.
So, reliance on conceptual understanding is limited to a shallowness (“grossness”) of understanding reality: limited awareness – Sem. A depth (“subtlety”) of understanding is encountered through non-conceptual knowing: pure awareness Rigpa.
Yet it also seems that “non-duality” may not even be experienced (maybe not the right word, but whatever) through non-conceptual knowing like simple perception or bare attention to experience… these could be seen as simply non-conceptual forms of Sem; not clearly knowing the totality of conceptual and non-conceptual awareness of presence (Rigpa).
Awareness itself (pure awareness of presence; reflexive deep awareness; self-arising deep awareness; awareness of its own face) seems to be the “place” where concept and non-concept can be subsumed (the way sunlight both clearly reveals objects and illuminates itself: clear light cognition that knows its “both-nature”) rather than used as markers of what is “real” or not.
[Rigpa aspects: primally pure awareness — self- and other-voidness, spontaneous awareness of pure appearances (clearly knowing), and responsive (compassionate) awareness]
[Rigpa types: Basis awareness, effulgent awareness, and essence awareness — compare with purgative, illuminative, and unitive and/or active, active-contemplative, and contemplative life]
Who the hell knows…