Actually what he described is the basis for Fiat money systems everywhere. As long as the government demands that all entities doing business pay a tax in dollars, the dollars will be worth something to those entities. (It's worth freedom to do business.)
Therefore the integrity of the financial system requires that there be a different ultimate form of backing, such as the acceptability of the fiat currency in payment of tax.
From Wikipedia: http://en.wikipedia.org/wiki/Fiat_currency
The unifying feature of all fiat money is its (typically exclusive) acceptability to the government for payment of taxes.
And yet again: http://www.absoluteastronomy.com/topics/Fiat_currency
Therefore the integrity of the financial system requires that there be a different ultimate form of backing, such as the acceptability of the fiat currency in payment of tax.