“Reciprocity is the basis of each relationship as long as the values to be exchanged are left open to interpretation. Measurement is enforced only when relationships break up. Just think of divorce proceedings. Accordingly, measurement cannot only devalue the goods measured, but also a relationship.”

The Truth: An Uncomfortable Book About Relationships (2015)

Diary of an Unknown (1988)

Oscar Iden Lecture Series, Lecture 3: "The State of Individuals" (1976)

Source: The Principles of Political Economy and Taxation (1821) (Third Edition), Chapter I, Section I, On Value, p. 5

Solved:The Mystery of Life

Source: The Wealth of Nations (1776), Book I, Chapter V.
Context: Every man is rich or poor according to the degree in which he can afford to enjoy the necessaries, conveniences, and amusements of human life. But after the division of labour has once thoroughly taken place, it is but a very small part of these with which a man's own labour can supply him. The far greater part of them he must derive from the labour of other people, and he must be rich or poor according to the quantity of that labour which he can command, or which he can afford to purchase. The value of any commodity, therefore, to the person who possesses it, and who means not to use or consume it himself, but to exchange it for other commodities, is equal to the quantity of labour which it enables him to purchase or command. Labour, therefore, is the real measure of the exchangeable value of all commodities.

Source: On Becoming a Person: A Therapist's View of Psychotherapy

Remarks by President Obama in Address to the United Nations General Assembly (24 September 2013) http://www.whitehouse.gov/the-press-office/2013/09/24/remarks-president-obama-address-united-nations-general-assembly
2013