"How do I know, for I am Caesar."  Who wrote these words and from what text?

The full quote is: 

"Beware the leader who bangs the drums of war in order to whip the
citizenry into a patriotic fervor, for patriotism is indeed a
double-edged sword. It both emboldens the blood, just as it narrows
the mind. And when the drums of war have reached a fevered pitch and
the blood boils with hate and the mind has closed, the leader will
have no need in seizing the rights of the citizenry. Rather, the
citizenry, infused with fear and blinded by patriotism, will offer up
all of their rights unto the leader and gladly so. How do I know? For
this is what I have done. And I am Caesar"

This is often claimed to have been spoken by Julius Caesar himself, or
to be from Shakespeare's play, "Julius Caesar."  All the information I
have been able to find however, says that it is bogus and was never
spoken by either the real Caesar or Shakespeare's.

http://www.shakespeare.com/queries/display.php?id=3168
http://www.geocities.com/anamericandreams/Caesar.html

Gremmy

As usual, Gremmy is on target. 

I doubt that the actual source of this fake quote will ever be found.
The "quote" spread like wildfire last year on the Internet. At least a
dozen friends emailed it to me, asking if I knew the context in which
Julius Caesar had written this (and, of course, I didn't know, since
there is no evidence that Caesar had any connection with the quote.)

For more info, here's an article from Snopes.com, the Web's most
popular source of information about hoaxes and urban legends:

http://www.snopes.com/quotes/caesar.htm