But as a head of state sworn to protect and defend my nation, I cannot  be guided by their examples alone. I face the world as it is, and cannot stand idle in the face of threats to the American people. For make no mistake: evil does exist in the world. A non-violent movement could not have halted Hitler's armies. Negotiations cannot convince al Qaeda's leaders to lay down their arms. To say that force is sometimes necessary is not a call to cynicism - it is a recognition of history; the imperfections of man and the limits of reason.