“Agriculture is a trade with the purpose… to produce profit or to gain money. The higher this benefit in the long run, the more complete this purpose is fulfilled.”

Commencement speech, Stanford University (2007-06-17)
Speeches and lectures

The portion of this statement, "Love is the only sane and satisfactory answer to the problem of human existence" has been widely quoted alone, resulting in a less reserved expression, and sometimes the portion following it has been as well: "Any society which excludes, relatively, the development of love, must in the long run perish of its own contradiction with the basic necessities of human nature."
The Art of Loving (1956)
Context: Our society is run by a managerial bureaucracy, by professional politicians; people are motivated by mass suggestion, their aim is producing more and consuming more, as purposes in themselves. All activities are subordinated to economic goals, means have become ends; man is an automaton — well fed, well clad, but without any ultimate concern for that which is his peculiarly human quality and function. If man is to be able to love, he must be put in his supreme place. The economic machine must serve him, rather than he serve it. He must be enabled to share experience, to share work, rather than, at best, share in profits. Society must be organized in such a way that man's social, loving nature is not separated from his social existence, but becomes one with it. If it is true, as I have tried to show, that love is the only sane and satisfactory answer to the problem of human existence, then any society which excludes, relatively, the development of love, must in the long run perish of its own contradiction with the basic necessities of human nature. <!-- p. 111 - 112

Guidon v. Robson (1809), 2 Camp. 304.

Source: The Wheel of Time: Shamans of Ancient Mexico, Their Thoughts About Life, Death and the Universe], (1998), Quotations from "The Power of Silence" (Chapter 18)

Source: The Principles of Agriculture, 1844, Section I: The fundamental principles, p. 1.

Source: The Path to Enlightenment is not a Highway, 1996, p.2

State of the Art (2000)

Good Company. The Study Society. 2009

Source: (1776), Book IV, Chapter I, p. 471.