Neidan Dictionary

⊛ Laozi and the Buddha used the learning of xing (inner nature) and ming (destiny, existence) to open the gates of expedient methods (fangbian), and taught people to cultivate the seed in order to escape [the cycles of] birth and death. 老釋以性命學，開方便門，教人修種，以逃生死。 (Awakening to Reality, Preface)

⊛ The creations and transformations brought about by Nature pertain to the mind. The creations and transformations brought about by Existence pertain to the body. Understanding and cognition emerge from the mind: with thoughts and cogitations, the mind yokes one’s Nature. Responses and reactions emerge from the body: with speech and silence, with sight and hearing, the body burdens one’s Existence. It is because Existence is burdened by the body that there are birth and death. It is because Nature is yoked by the mind that there are coming and going (i.e., the “coming and going” of thoughts). 性之造化系乎心，命之造化系乎身。見解知識出於心也，思慮念想心役性也。舉動應酬出於身也，語默視聽身累命也。命有身累，則有生有死。性受心役，則有往有來。 (Li Daochun, The Harmony of the Center: An Anthology, chap. 4)

⊛ What is Nature? It is what truly is as it is (zhenru) since the Original Commencement; it is the One Numen, luminous and bright. What is Existence? It is the precelestial perfect Essence; it is the One Breath, provided with its generative force. Therefore when there is Nature there is Existence, and when there is Existence there is Nature. Nature and Existence at the origin cannot be divided from one another. . . . Even more, Nature cannot be established without Existence, and Existence cannot be preserved without Nature. 何謂之性？元始真如，一靈炯炯是也。何謂之命？先天至精，一炁氤氳是也。然有性便有命，有命便有性。性命原不可分。. . . 況性無命不立，命無性不存。 (Principles of the Conjoined Cultivation of Nature and Existence)

⊛ Nature and Existence are the root and foundation of self-cultivation. 性命是修行之根本。 (Wang Chongyang, Fifteen Essays by Wang Chongyang to Establish the Teaching, trans. in Taoist Internal Alchemy: An Anthology of Neidan Texts, p. 159)

⊛ The secret of the Golden Elixir only consists in Nature and Existence. 金丹之秘，在於一性一命而已。 (Qiu Chuji, attr., Straightforward Pointers on the Great Elixir)

⊛ The essential for refining the Elixir only consists in the words “Nature” and “Existence”. 煉丹之要，只是性命兩字。 (Li Daochun, The Harmony of the Center: An Anthology, chap. 3)

⊛ Indeed, the Way of the Golden Elixir consists in the Way of cultivating Existence and cultivating Nature. The Way of cultivating Existence is the Way of “doing” (youzuo), the Way of cultivating Nature is the Way of “non-doing” (wuwei). 蓋金丹之道，一修命、一修性之道。修命之道，有作之道，修性之道，無為之道。 (Awakening to Reality, "Cut-off Lines", poem 42 Comm. Liu Yiming)

⊛ What should be investigated does not lie outside of the words “Nature” and “Existence”. 究之不外乎性命二字。 (Liu Yiming, Cultivating the Tao, chap.)