Lecture Notes on the Sūtra of the Collection of the Father and Son (Pitāputrasamāgamanasūtra) (I, II, III)

The equanimous mind is neither joyful nor distressed; it abides in a middle state detached from both extremes—neither craving nor averse, neither good nor bad, neither painful nor pleasant. At this time the mind is calm and without ripples, without highs and lows. For example, when you look at a person and feel nothing in particular—neither liking nor disliking them—that is the equanimous mind. If a mind of liking arises, then you experience pleasant feeling, a pleasant vedanā; if you feel this person is annoying, that is a painful feeling, and hatred has emerged. Therefore feelings are of three kinds: painful feeling, pleasant feeling, and the neutral feeling (upekṣā-vedanā) that is neither painful nor pleasant.

As for the sound of equanimity, it refers to sounds that belong neither to the wholesome nor to the unwholesome, abiding in a middle state that is neither good nor bad. If in a dream a person hears others speaking words that do not form coherent sentences, meaningless words, and although he does not feel anything particular about them in his mind, he takes them to be real things and keeps recollecting them repeatedly. Even if one clings to this state of equanimity as truly existent and craves this equanimous thought, not knowing that the six sense objects of equanimity are equally illusory, one still does not escape birth and death.

The "indefinitive statements" (不了义句) here are different from the "indefinitive sūtras" (不了义经) in the Buddhist scriptures; they are not the same thing. Buddhist sūtras are divided into definitive sūtras (了义经) and indefinite sūtras (不了义经). Definitive sūtras are true, expounding the real dharma; indefinite sūtras do not expound the real dharma. Definitive sūtras teach the Mahāyāna scriptures on the ultimate truth of tathāgatagarbha—this is called definitive (了义), the fundamental dharma, the dharma of true reality. Other scriptures, those that do not expound the dharma of tathāgatagarbha, are not definitive sūtras. Those that do not expound the dharma of our true mind, the tathāgatagarbha, are indefinite, not fundamental scriptures. Of course, within definitive sūtras there are also indefinite statements, and within indefinite sūtras there are even more indefinite statements.