A recent paper quantifying the degree of inbreeding among the Spanish Hapsburg dynasty - quite interesting even if you're not personally into inbreeding - led me to spend some time reading up on insane and retarded rulers. One thing that struck me is how few of these reigns were actually disastrous - it seems that most of the time regents, advisors, queen mothers etc. kept the country running along with the crazy idiot on the throne. It seems that monarchy evolved remarkably robust ways of dealing with utter incompetents who theoretically possess absolute power. Hell, Fyodor I was a generally admired and popular ruler in Russia.

Yet, the disability of Charles II of Spain did cause his country and others enormous problems. He precipitated the War of Spanish Succession not by being a bad ruler but by being really, really lousy in bed.

For 10 years, the couple struggled in vain to beget a child. It seems that, although Carlos attempted intercourse, he suffered from very premature ejaculation, so that he was unable to achieve penetration. Marie Louise confided in the French ambassador, that "she was really not a virgin any longer, but that as far as she could figure things, she believed she would never have children". The French ambassador even managed to get a pair of Carlos' drawers and had them examined by surgeons for traces of sperm, but the doctors could not agree about their findings.

His second wife did no better. So, here is the fatal flaw of monarchy and the major advantage of democracy. Democracy is, as far as I can tell, completely immune to disasters caused by the premature ejaculation problems of its rulers.