小布什总统时代的国防部长拉姆斯菲尔德以善于诡辩著称。他在为发动伊拉克战争辩解时说过一句非常有名的诡辩词:“这世上有已知的已知,也就是我们知道我们知道。这世上也有已知的未知,也就是我们知道我们不知道。这世上还有未知的未知,也就是我们不知道我们不知道。”(“there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns -- the ones we don‘t know we don’t know.”)