"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 origin of this has been the source of some speculation:
According to some slight research that I conducted today on the
subject, this quote appears to be a paraphrase of the following:
"He [Lysander] procured the abrogation of that ancient law which
prohibited the importation of gold into the republic. It was not
allowed a free circulation, but was deposited in the public treasury,
to be employed solely for the uses of the state. It was declared a
capital offence if any should be found in the possession of a private
citizen. Plutarch censures this as a weak and sophistical distinction.
It was indeed easy to see, that whenever it became necessary for the
state to be rich, it would soon become the interest and the passion of
individuals to be so. This consequence immediately followed; and
though some severe examples were made of offenders against the law, it
was found impossible, from this period, to enforce its observance."
From Tytler's Universal History, Vol.1, Chapter II, p.153.