Alan Greenspan explains it in this short six page summary
Gold and economic freedom
Editor's note - It may surprise more than a few gold devotees to learn they have an ideological friend in none other than Federal Reserve Board chairman Alan Greenspan. Starting in the 1950s, in fact, Greenspan was a stalwart member of Ayn Rand's intellectual inner circle. A self-designated "objectivist", Rand preached a strongly libertarian view, applying it to politics and economics, as well as to religion and popular culture. Under her influence, Greenspan wrote for the first issue of what was to become the widely-circulated Objectivist Newsletter. When Gerald Ford appointed him to the Council of Economic Advisors, Greenspan invited Rand to his swearing-in ceremony. He even attended her funeral in 1982. In 1967, Rand published her non-fiction book, Capitalism, the Unknown Ideal. In it, she included Gold and Economic Freedom, the essay by Alan Greenspan which appears below. Drawing heavily from Murray Rothbard's much longer The Mystery of Banking, Greenspan argues persuasively in favor of a gold standard and against the concept of a central bank.
http://www.usagold.com/publications/greenspan.pdf