From Alexander Tyler, a history professor at the University of Edinburgh. Written in 1787:
A democracy is always temporary in nature; it simply cannot exist as a permanent form of government. A democracy will continue to exist up until the time that voters discover that they can vote themselves generous gifts from the public treasury. From that moment on, the majority always votes for the candidates who promise the most benefits from the public treasury, with the result that every democracy will finally collapse due to loose fiscal policy...which is always followed by a dictatorship.
The average age of the worlds greatest civilizations from the beginning of history, has been about 200 years. During those 200 years, these nations always progressed through the following sequence:
1. From bondage to spiritual faith;
2. From spiritual faith to great courage;
3. From courage to liberty;
4. From liberty to abundance;
5. From abundance to complacency;
6. From complacency to apathy;
7. From apathy to dependence;
8. From dependence back into bondage
UPDATE: See Catherine's comment below for a question about the accuracy of this quote. Thanks, Catherine!