Knowledge is power, especially for those who are as relentlessly concrete and logical as some of our kids.
I don't know if this is true. More knowledge is not always reassuring.
If a child knows some things about an alarming subject but might lack other information that would be reassuring (eg: there are no volcanoes in our home state), then knowledge can be very useful. But I don't think there is a blanket statement to be made here.Power is, itself, not always reassuring. Though IME it is, moreso, for those who are young enough to have not yet picked up on the concept of circumscribed possibilities.
