“Economic power is exercised by means of a positive, by offering men a reward, an incentive, a payment, a value; political power is exercised by means of a negative, by the threat of punishment, injury, imprisonment, destruction. The businessman's tool is values; the bureaucrat's tool is fear.”

Mittel Energie auszuüben und nur ihn anzuordnen der Energie besitzt kann sie ausüben. Dieser direkte Anschluß der Energie und der Richtlinie bildet die grundlegende Wahrheit aller Politik und den Schlüssel zu aller Geschichte.
As quoted in The German Idea of Freedom : History of a Political Tradition (1972) by Leonard Krieger, p. 354

Introduction
Capitalism and Freedom (1962)
Context: The free man will ask neither what his country can do for him nor what he can do for his country. He will ask rather "What can I and my compatriots do through government" to help us discharge our individual responsibilities, to achieve our several goals and purposes, and above all, to protect our freedom? And he will accompany this question with another: How can we keep the government we create from becoming a Frankenstein that will destroy the very freedom we establish it to protect? Freedom is a rare and delicate plant. Our minds tell us, and history confirms, that the great threat to freedom is the concentration of power. Government is necessary to preserve our freedom, it is an instrument through which we can exercise our freedom; yet by concentrating power in political hands, it is also a threat to freedom. Even though the men who wield this power initially be of good will and even though they be not corrupted by the power they exercise, the power will both attract and form men of a different stamp.

Source: Politics Among Nations (1948), p. 27 (1954 edition).
Context: We must distinguish between military and political power.
Political power is a psychological relation between those who exercise it and those over whom it is exercised. It gives the former control over certain actions of the latter through the influence which the former exert over the latter's minds. That influence may be exerted through orders, threats, persuasion, or a combination of any of these.

Source: J. A. Hobson's Imperialism: A Study: A Centennial Retrospective (2002), p. 3-4.

Entre Nous, p. 2
My Years As Prime Minister (2007)

Source: 1970s-1980s, The Limits Of Organization (1974), Chapter 1, Rationality: Individual And Social, p. 16

Source: Politics Among Nations (1948), p. 27 (1954 edition)

Source: Why Men Are the Way They Are (1988), p. 103.

My Disillusionment in Russia (1923)