About the time our original thirteen states adopted their new constitution in 1787, Alexander Tyler, a Scottish history professor at the University of Edinburgh, had this to say about the fall of the Athenian Republic some 2,000 years earlier:
"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 they can vote themselves generous gifts from the public treasury.
"From that moment on, the majority always vote 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 world's greatest civilizations have been about 200 years;
"During those 200 years, those 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"
And goes on to other things. It is incorrect. But the misinformation doesn't appear to be wholly intentional. There was no Alexander Tyler at Edinburgh at that time. However, there was an Alexander Fraser Tytler, more formally known as Lord Woodhouselee, who was a historian; and earlier forms of the attribution do quite explicitly assign it to him. The quotation in question is not in any of his works, however.
It turns out that no one knows who originally said it. Loren Collins has done some research into the provenance of this quotation; apparently the first person known for sure to have attributed the first part of the quote to Woodhouselee was Ronald Reagan. It's a mystery where he got the attribution from; prior to Reagan, the quotation is attributed to the Usual Suspects, people like Macauley and Alexis de Tocqueville, who tend to be assigned quotations of unknown origin. Since Tytler is certainly not one of the Usual Suspects, and since he was certainly a real person, Reagan couldn't have just pulled his name out of thin air.
And in fact, if you read what Woodhouselee says about Athenian democracy in his Universal History, the mystery thickens. He's very critical of the notion of democratic government; he thinks that pure democracies don't exist (which is not really very controversial), that in mixed democracies the sovereignty of the people is simple illusory (which is a bit more controversial), that the Montesquieu-style claim that virtue is the principle of democratic government is mere utopianism, that the idea that men in a democracy love equality is blatantly false, that the reason you find such notable extraordinary examples of patriotic virtue under democratic governments is that such governments impede virtue (so any virtue that can be noticed will have to be extraordinary), and so forth. So although Woodhouselee does not appear to have ever said the first half of the quote (from "A democracy..." to "...a dictatorship") it's not a wholly implausible thing to attribute to him. (The second half appears to be a completely different quotation spliced onto the first quotation.) But it appears that this means that someone at some point who had read Woodhouselee's Universal History would have had to misattribute a quotation to him that was already floating around. That's an odd thing to happen.
An interesting, and as yet unresolved puzzle. In any case, thanks to the Internet Archive, you can read some of Alexander Fraser Tytler's works online. He's a resource for understanding the Scottish Enlightenment because he wrote a biography of Lord Kames, whom he had known personally; Kames, also called Henry Home, was a major player in the Scottish Enlightenment, as were his cousins John Home and David Hume.