Thanissaro Bhikku wrote:
Emptiness as a quality of dharmas, in the early canons, means simply that one cannot identify them as one’s own self or having anything pertaining to one’s own self… Emptiness as a mental state, in the early canons, means a mode of perception in which one neither adds anything to nor takes anything away from what is present, noting simply, “There is this.” This mode is achieved through a process of intense concentration, coupled with the insight that notes more and more subtle levels of the presence and absence of disturbance.
(Wikipedia, “Sunyata” entry as of Sept. 19, 2020)
I don’t recall mention of emptiness in the first four sets of volumes of the Pali Canon sermons, the books which I think constitute the “early canons”. The attribution of meaning to emptiness by Thanissaro appears to me to be entirely his own, as is his description of a method by which his notion of a goal might be achieved.
This is what I recall:
Whatever… is material shape, past, future or present, internal or external, gross or subtle, mean or excellent, or whatever is far or near, (a person), thinking of all this material shape as ‘This is not mine, this am I not, this is not my self’, sees it thus as it really is by means of perfect wisdom. Whatever is feeling… perception… the habitual tendencies… whatever is consciousness, past, future, or present (that person), thinking of all this consciousness as ‘This is not mine, this am I not, this is not my self’, sees it thus as it really is by means of perfect wisdom. (For one) knowing thus, seeing thus, there are no latent conceits that ‘I am the doer, mine is the doer’ in regard to this consciousness-informed body.
(MN III 18-19, Pali Text Society III pg 68)
In my piece Letting Go in Action, I say this about “perfect wisdom”:
“By means of perfect wisdom” is an affirmation that seeing through the conceit “mine is the doer” depends on a knowledge inherent in human nature, a knowledge that escapes the use of reason.
I say that because until a person experiences action of the body without the exercise of volition, they cannot find a way to believe it exists, even though they may have seen it in someone else during a performance of stage hypnosis or in the presence of someone like Kobun Chino Otogawa.
The practice of Gautama was the intent concentration on in-breaths and out-breaths, both before and after his enlightenment. That his observation of cause and effect could have been so selfless is the reason his descriptions have endured (but he also made mistakes as a teacher, as when his “meditation on the unlovely” resulted in the suicide of scores of monks).
For me, “this is not mine, this am I not, this is not myself” is a a part of freeing the mind in an in-breath or an out-breath, and yet freeing the mind is preceded by composing the mind in an in-breath or out-breath: this is proprioception alongside of equalibrioception as a nececessity in the movement of breath, and the experience of detachment and the cessation of volition in an in-breath or out-breath can take place out of necessity in an in-breath or out-breath. Mindfulness of detachment and mindfulness of the cessation of volition constitute the fourteenth and fifteenth aspects of Gautama’s practice, preceded by mindfulness of composing the mind, of freeing the mind, and of impermanence.
Deliverance from thought without grasping is non-thinking, but in this consciousness-informed body there can be no doer of non-thinking; it’s a matter of relaxed necessity in the movement of breath.