By David Ignatius WASHINGTON -- A disease is eating away at the Middle East. It afflicts the Syrians, the Iraqis, the Lebanese, even the Israelis. It is the idea that the only political determinant in the Arab world is raw force -- the power of physical intimidation. It is politics as assassination. This week saw another sickening instance of this law of brute force, with the murder of Pierre Gemayel, a Lebanese Cabinet minister who had been a strong critic of Syria. Given the brutal history of Syria's involvement in Lebanon, there's an instant temptation to blame Damascus. But in this land of death, there are so many killers and so few means of holding them to account, we can only guess at who pulled the trigger. I fell in love with Lebanon the first time I visited the country 26 years ago. Part of its appeal, inevitably, was the sense of living on the edge -- in a land of charming, piratical characters who cherish their freedom. Lebanon has great newspapers, outspoken intelle...