In a capitalist society, all human relationships are voluntary. Men are free to cooperate or not, to deal with one another or not, as their own individual judgments, convictions, and interests dictate. They can deal with one another only in terms of and by means of reason, i.e., by means of discussion, persuasion, and contractual agreement, by voluntary choice to mutual benefit. The right to agree with others is not a problem in any society; it is the right to disagree that is crucial. It is the institution of private property that protects and implements the right to disagree—and thus keeps the road open to man’s most valuable attribute (valuable personally, socially, and objectively): the creative mind.

- Ayn Rand. Capitalism: The Unknown Ideal (1966).