For want of a butterfly the nail was driven into the tree with a cheetah in it. Or something like that.

You may have heard of the “butterfly effect” in chaos theory, the notion that even a tiny change in initial conditions can result in a huge difference in a later state that follows from those initial conditions — e.g., a butterfly flapping its wings could ultimately affect the formation-time and the exact path of a tornado in a distant place.

Or perhaps you’ve run across some form or another of this little ditty:

For want of a nail the shoe was lost,
for want of a shoe the horse was lost,
for want of a horse the knight was lost,
for want of a knight the battle was lost,
for want of a battle the kingdom was lost.
So a kingdom was lost—all for want of a nail.

I thought of that nail and that butterfly last night, while reading an article in National Review by the writer David Mamet.  He was discussing the concept of  “the accident chain,” which, he says, is part of the jargon of “transportation-safety folks.”  He gives two examples — this one:

The mother was driving her small child to school. She was buckling her into the car seat when she heard the tea kettle whistling in the house. She’d neglected it be­cause, when she was making the tea, the phone rang. When she got off the phone she was late, and so she rushed her child into the car, forgot she’d left the kettle on, and went back into the house to turn it off.

She was driving her toddler to school, the kid started to climb into the front seat because the mother had forgotten to buckle her in. The mother turned around to secure the kid and ran into a tree. Where did the accident chain begin?

And this one:

Army aviators, returning from the First World War, brought back the French affectation of flying with exotic feline cubs as pets. A barnstormer flew with his pet cheetah up front until the creature got too big for his lap, when he transferred it to the rear seat. The cheetah enjoyed flying, as the hum and the vi­bration put him to sleep. One day the cat, now fully grown, slipped, asleep, off the rear seat and jammed himself against the stick; the pilot, up front, thus had his stick (linked to the rear) immobilized, and flew into the ground.

Why did the pilots fly with exotic cubs?

French law prohibited foreign nationals from service in the French armed forces. Before our entry into the war, Americans who wanted to fly for France were inducted into the French Foreign Legion — a service exempted from restriction.

The Legion saw extensive service in Africa, where its officers adopted the habit of exotic pets. Did the barnstormer die because the French colonized much of Africa? Of course/certainly not.

If you believe that our thoughts are produced by, and are thus reducible to, chemical effects in our brains, then, very arguably, they become simple links in a chain of chemical reactions extending backward to the very origins of chemistry immediately following the Big Bang and forward, without meaningful freedom, to the massive heat death of the universe.

You decide to marry Britney.  You choose to take the job in Chicago.  You put your money on Natural Charm in the fourth.  You declare a major in biology.  Where did the decision chain begin?  Roughly 13.7 billion years before the present.