Therefore then, Subhuti, the Bodhisattva should produce an unsupported thought, a thought which is nowhere supported, which is not supported (apratisthiti) by forms, sounds, smells, tastes, touchables, or objects of mind.
A thought is “Unsupported” because it does not arise in dependence upon anything else, not “caused” by another thought (“mind-objects”) and of course not “produced” by a thinker, which the Bodhisattva realizes does, not exist. Such an “unsupported thought”, then, is prajna, arising by itself nondually. (Intuiton)
Hui Neng’s grandson in the Dharma, Ma-tsu, reinforces Hui Neng and the Diamond Sutra: “So with former thoughts, later thoughts, and thoughts in between: the thoughts follow one another without being linked together. Each one is absolutely tranquil”. That each such “unsupported thought” is absolutely tranquil is a new point, although probably implied by Hui Neng’s term “thoughtlessness”.
So when one loses sense of self and completely becomes an unsupported thought, there is the Taoist paradox of wei-wu-wei, in which action and passivity are combined: there is the movement of nondual thought, but at the same time there is awareness of that which does not change. That is why such an experience can just as well be described as “thoughtlessness”. The later Ch’an master Kuei-shan Ling-yu referred to this as “thoughtless thought”: “Through concentration a devotee may gain thoughtless thought. Thereby he is suddenly enlightened and realizes his original nature”. “Thoughtless thought” is not a mind empty of any thought: “one thought is thoughtless thought.“
An important parallel to this is found in the writings of a modern Advaitin, Ramana Maharshi:
The ego in its purity is experienced in the interval between two states or between two thoughts. The ego is like the worm which leaves one hold only after it catches another. Its true nature is known when it is out of contact with objects or thoughts. You should realize this interval as the abiding, unchangeable Reality, your true Being…