German authorities say there is no link between Islamic terrorism and a man who stabbed four people at a train station Tuesday. The attacker is just mentally ill, they explain.

But during the assault, he yelled “infidel, you must die” and “Allahu akbar.”

Of course he is mentally ill. But so, in a very real way, is anyone else involved in terrorism. Nidal Hassan, who killed 13 people at the Fort Hood, Texas, Army base in 2009, comes to mind.

There is another explanation for many terrorist attacks, of course: pure evil.

Attempting to minimize the threat of Islamic terrorism by blaming some attacks on mental illness is absurd and intellectually dishonest. Of course there is a link.