For those that may be curious, the quotes I have started posting are from my current reading, pretty much posted as I come to them. They are passages that jump out at me as I go along.
This particular quote is from Ayn Rand's book "Capitalism: The Unknown Ideal" and is in the section discussing reason as man's means of survivial. As she says a bit earlier: "The action required to sustain human life is primarily intellectual: everything man needs has to be discovered by his mind and produced by his effort." You have only to look around and see all things that are needed to allow man to survive in the world (food, shelter, clothing, defense, and etc) and enjoy life (books, movies, music, travel, and etc) to see that this is true.
"Since knowledge, thinking, and rational action are properties of the individual, since the choice to exercise his rational faculty or not depends on the individual, man's survival requires that those who think be free of the interference of those who don't. Since men are neither omniscient nor infallible, they must be free to agree or disagree, to cooperate or to pursue their own independent course, each according to his own rational judgement. Freedom is the fundamental requirement of man's mind."