A useful if tongue-in-cheek definition. With thanks to The Onion, Inc., copyright 2012.
From The Onion Book of Known Knowledge: a Definitive Encyclopaedia of Existing Information in 27 Excruciating Volumes, Little, Brown and Co., NY (2012)
Judaism, world religion whose central tenant implores believers to stick together because someone is currently trying to kill them. Jewish theology is rooted in the covenant between God and the children of Israel, who are commanded by the Torah never to get too comfortable, as there are already plans in motion for their murder and the murder of their families. Since Jews never know exactly who is out to assassinate them, when it will happen, or how, Jewish tradition includes the constant retelling of previous atrocities as a means of maintaining group preparedness and of terrifying the younger generation into internalizing the very real possibility of having to grab their siblings at a moment’s notice and hide out in the woods until it’s safe to escape on foot. Although Judaism consists of several denominations with different conceptions of spirituality and culture, all Jews affirm the core doctrine of always sleeping lightly because someone who wants to shoot them in the head is closing in.