Takfirism is the ideological underpinning of and justification for Al Qaeda’s attacks on us, including on that September 11 six years ago. We have erred for six years in not identifying that ideology plainly, in a struggle that is above all else an ideological one. It is critical that we do so not only for our own people, but for many millions of Muslims who are our potential allies in the struggle, but who are wary of our intentions and are bombarded by propaganda from at home claiming we fight for oil or from abroad claiming we seek to destroy...