Go ahead, picture a religious Jew.

Now picture a Muslim cleric.

Now an Amish farmer.

What do they have in common? Beards. And not neatly trimmed beards, but, in the popular stereotype, long, unruly beards, which connote piety, spiritual intensity and a life so hard at study that there is no time for a shave. The scholar, the mystic, the terrorist, the holy man