Righting the Ship of State
One of the most prominent critics of democracy was, of course, Plato, who along the way gave us the metaphor of "the ship of state." Democracy, he argued, was akin to a ship being steered and navigated by the passengers. Different potential captains would sell themselves to the passengers by pandering to their desires rather than based upon their seamanship. Such a voyage could not but end badly, Plato thought. The argument for a mixed constitution flows pretty naturally from this metaphor, I think, although Plato did not pursue it in that direction. While it's true we don't want the passengers picking which channel to attempt or when to tack, we also don't fancy the notion of the captain essentially kidnapping the passengers and dragging them anywhere on the seven seas he wishes to go. A mixed constitution tries to balance sound seamanship and individual autonomy.