We differentiate between situations in which someone is to blame and those in which no one is to blame, that's all. If we didn't do that, we'd either have to blame the elements or excuse deliberate wrong-doing. Well, both of these things are sometimes done, but only in the way of obscuring how the world works.Whilst I too find the differentiation in question flawed and potentially dangerous, I wish that at other times – and the topic of "tragedy" is an excellent instance – we were a little more rather than less differentiated.
For instance, I wonder whether the term "tragedy" ought to be used for the examples discussed by Norm at all. These days, unfortunately, the term tragedy has become the default descriptor for most aspects of human experience, from genocide to teenage obesity, and I believe that this is part of the problem addressed here.
I think it's about time we refined our own lackadaisical use of the concept of tragedy, for instance by returning to its roots in classical theatre.
In Aristotle's theory of tragedy, few plots and topics are truly tragic. Natural disasters, for instance, don't come under the headword "tragedy", as they are the result of an overriding force - call it contingency, call it fate - beyond the reach of the individual. Terrorist attacks differ from this kind of disaster only in so far that they are historical, man-made and somewhat more selective.
Otherwise, both types of catastrophes are similar in their indifference and their effect: they are reminders of the terrible coincidences that determine human existence: the frightening fact that for as long as we live we are always potentially in the wrong place at the wrong time.
This is terrible indeed, but it is clearly not tragic in the strict sense of the term, nor are the victims of this terrible contingency tragic heroes. The tragic hero in Aristotle's theory - always an exceptional human being, but morally a mutt (neither entirely bad nor completely good) - is the victim of his/her own misguided actions of which he/she is crucially unaware. His/her destruction is brought on by the tragic flaw that marks his/her character, be that blindness or hubris or a mixture of both.
Can we say this of the people who die in a natural catastrophe? Is this true of people who unknowingly board a plane/train/bus with a person who has a belt of explosives strapped around her or his waist? And what do we gain by calling these events and their victims "tragic"? What do their victims (or their loved ones) gain from this label?
As far as the victims of such events go, nothing. Quite to the contrary, by labelling their deaths "tragic" and lifting them onto a level of transcendent significance, we only deny what makes death - theirs and ours - so terrible in the eyes of the living: its meaningless immensity.
The winners of this discourse are those who live to apply the label. Like all euphemisms, the term tragedy is ahistorical, providing a cover for sanctimonious displays of extreme emotion that allow us to deny life's murky realities and ignore the true terror of human existence - in other words: make us feel great.