Jeff Franks wrote:

"A democracy cannot exist as a permanent form of government. It can only
exist until the voters discover that they can vote themselves money from the
public treasure. From that moment on the majority always votes for the
candidates promising the most money from the public treasury, with the
result that a democracy always collapses over loose fiscal policy followed
by a dictatorship.
The average age of the world's great civilizations has been two hundred
years. These nations have progressed through the following sequence: from
bondage to spiritual faith, from spiritual faith to great courage, from
courage to liberty, from liberty to abundance, from abundance to
selfishness, from selfishness to complacency from complacency to apathy,
from apathy to dependency, from dependency back to bondage. "

Alexander Tyler - Circa 1780 - discussing the fall of the Athenian
Democracy.

Snopes (the Urban Legend site) lists this as probably a fictitious
quote. See http://www.snopes.com/politics/quotes/tyler.asp for details.