9/11 at 21: We still must remember and still must beware

At some point, annual remembrances of tragic events can get old. The 21st anniversary of the 9/11 terrorist attacks might seem like a good time to let the anniversary go unremarked — never even close to forgotten, of course, but no longer treated as a front-burner topic.

A back-burner treatment, though, would be a mistake.

In addition to wanting to remember those who died and those who acted heroically, there is a very practical reason we should keep the terrorism on 9/11 fresh in our minds. We should do so...