The Tao Teh King: A Short Study in Comparative Religion, by C. Spurgeon Medhurst, , at sacred-texts.com
Thirty spokes meet in one hub, but the need for the cart existed when as yet it was not. Clay is fashioned into vessels, but the need for the vessel existed when as yet it was not. Doors and windows are cut to make a house, but the need for the house existed when as yet it was not. Hence there is a profitableness in that which is and a need in that which is not. 1
19:1 This chapter teaches that the real usefulness of everything lies in the original noumenal conception.
Hsüeh-kün-ts’ai says—"Although substance and the accidental are ever changing places, the intention is to make that which is the visible (accident) express that which is invisible (substance). Everyone knows the advantage of the visible, but who searches for the usefulness of the invisible, and hence Lao Tzu illustrates the matter as in the text."
Says Tung-tei-ning—"This chapter shows that while substance has form its usefulness lies in its essence; the noumenal and the phenomenal (lit. the empty and the real) continually revolve around each other, but while the latter has the advantage of being existent, its root lies in that which is (apparently) non-existence, and it is that which constitutes its usefulness." Cf. Notes to ch. 1.
Su Cheh has the following—"The ends of matter have been reached when it has been fashioned into form, but the usefulness of the form lies both in the phenomenal and in the noumenal. When it is not on the phenomenal plane it is on the noumenal, and its usefulness lies in its noumenon. When it is not on the noumenal plane it is on the phenomenal, and its profitableness is manifested by phenomena."
This teaching concerning the relations between concealed and revealed nature was also enunciated by Paracelsus; it is elaborated in the Sankhya philosophy of India; and was taught by the Hermetic philosophers of Greece.
Compare also the following explanation by Leibnitz—"The primitive element of every material body being force, which has none of the characteristics of matter—it can be conceived but can never be the object of any imaginative representation."
vid. "The Secret Doctrine," vol. i, p. 303; also chap. 49 of the Tao Teh King, where the reality of the phenomenal universe is described as unite meeting in unity—immaterial.