The Lives of the Twelve Caesars

"The termination of the civil war between Caesar and Pompey forms a new epoch in the Roman History, at which a Republic, which had subsisted with unrivaled glory during a period of about four hundred and sixty years, relapsed into a state of despotism, whence it never more could emerge. So sudden a transition from prosperity to the ruin of public freedom, without the intervention of any foreign enemy, excites a reasonable conjecture, that the constitution in which it could take place, however vigorous in appearance, must have lost that soundness of political health which had enabled it to endure through so many ages."