What is undistracted calm abiding? It is meditative absorption free of the six types of distraction. What are these six?
1. Inherent distraction refers to the eye consciousness and the other four collections of consciousness. Because they are naturally directed outward, they [cause one to] emerge from meditative absorption.
2. External distraction refers to a mental consciousness that reaches out towards or engages objects.
3. Internal distraction concerns dullness and agitation, as well as savoring one’s meditative absorption.
4. The distraction of marks occurs when, trusting in meditative absorption, one apprehends marks of it and becomes attached.
5. Distraction brought about by negative tendencies is when directing the mind involves the apprehending of an ego. This is said to refer to the mental act of pridefully believing oneself to be superior to others, or (simply any mental act) that involves apprehending an “I.”
6. The distraction of directing the mind occurs when one is caught up in the mindset of, and directs the mind in the style of, the Lesser Vehicle.
The undistracted calm abiding that is determined by the elimination of those six is the unique calm abiding of the Great Vehicle. This is a state of one-pointed inner rest, a flawless calm abiding. In it, there is no apprehension of marks, as is the case when inner absorption alone is believed to bring liberation. Neither does it involve the ego apprehension that occurs in the concentrations of non-Buddhists. Further, one does not direct the mind as one would when cultivating the supports for the inferior paths [to liberation]. This is how the wise should understand the calm abiding of the Great Vehicle.
— From Middle Beyond Extremes: Maitreya’s ‘Madhyantavibhaga’ with commentaries by Khenpo Shenga and Ju Mipham, translated by the Dharmachakra Translation Committee, published by Snow Lion Publications