Friday, 24 March 2006
We Don't Usually Electrocute Speakers We Like

The event will be recorded in our Center's calendar as Nancy Cartwright visiting in our Annual Lecture Series to speak on the topic of Hunting Causes and Using Them. That is how historical records strip the life out of real events.

It had a rocky start. We lost our usual room well after our regular announcements went out. So we sent out emergency notices about the room change and hoped everyone would hear. As we settled into our seats at the appointed hour, the strong attendance showed they had.  Brian Hepburn tinkered silently and swiftly with the last minute adjustments of the overhead projector, the lapel microphone and so on. I knew that his calm exterior masked the stress of setting up two unfamiliar rooms, one for the reception to follow.

"Where is the theory in our 'theories' of causality?" Nancy asked, as the talk began. In another room this would be idle chatter. In this room it was not. The audience was packed with people whose central professional interest lay in causation. Perhaps it was in the metaphysics of causation. Or they were part of efforts extending over decades to craft computer driven algorithms that bested humans in wrestling the causal structure from the clutches of sociological  data. She had their interest.

From my front row seat, I had an ideal line of sight to Nancy and the huge, glowing overhead projector screen behind her, on which the phrase "C causes E" shone. "Perfect," I thought, "All is shipshape...," at the very moment that the overhead projector emitted a pop and the screen went dark.

If this has never happened to you, you won't understand the awful, empty feeling. It is something like the dream we all have of standing up in the cavernous hall to give that speech and realizing that you are still dressed in your pjamas--the ones with the teddy bears. Or in this case, you have pulled hard on every tigers' tail and, just as they lock their yellow eyes on you, you pull on the rope that leads up out of pit and it falls broken at your feet.

A knowing look passed over Brian's face and he swept out of the room.  It took me a moment longer before I remembered the slide that engages the backup bulb. I crept around to the front of the projector and slid it over--that one was burnt out too.

Nancy kept going. "I don't need the projector for this." Her worry about causation was simply stated. We want a theory of causation that both lets us hunt causes and use them. That is, it must give us the means to find causes and know that we have found them. And it must also assure us that causal knowledge is a useful thing to have. We must be able to do things in the world with it. We have many theories of causation. All of them are terrific at one. None are good at both.

That was a claim that really needed to be illustrated. The illustrations were complicated and our chalkboard sufficed for a few simple formulae. Now Nancy really did need more. Cecil B. De Mille could not have scripted it better. The door opened and in walked Brian carrying an overhead projector. There is a curious phenomenon in which an entire crowd, unwittingly and without prior planning,  sighs like a great beast exhaling. It sighed. The table at the front was hastily reorganized and the lectern shoved over to make room. Soon Nancy had pulled out transparencies and covered the screen with words and formulae.

There were many examples, some complex, some not. One especially simple one seemed to express the worry very nicely. If this follows that, should we say that this caused that? Daylight follows night; so does night cause daylight? No one finds that plausible. For this to cause that, there has in addition to be some power that this exerts on that. In manipulation theories of causation, we identify that extra piece with the fact that changing the cause lets us manipulate  the effect. The gas causes the gaslight; more or less gas produces more or less light.

Nancy was on a roll. Nothing would derail her. Not even a loud BOOM. She had stepped on the wire trailing from her lapel microphone so it had fallen to the table. After a moment's confusion, she collected the microphone and her thoughts and continued.

So manipulation theories excel in the "use" area. Once we know the causes of things, we can _use_ those causes to manipulate them. It's automatically so in this theory. But this manipulation theory gives us no hint on how to find causes. There are no markers independent of the use of causes. That issue of independence seemed to me to lie behind Nancy's deeper worry. She had no qualm over the idea that there are ways in the world that we can manipulate things. But calling it "causation" adds nothing to the idea of manipulation and is even positively misleading if you now come to think that you have forged a connection with all the other things that you call "causation" under the aegis of the many different theories of causation.

Nancy did have a deeper worry at this point, but that was not it. She was worried about a powerful tingling sensation in her feet and creeping up her legs. There are things that cannot long be ignored. Looking down, she gasped "Oh--there's a puddle of water." Then it all fell into place. When the table had been rearranged, a glass of water had been knocked over. The trailing wire from her microphone now ran through the water. Brian later explained to me that the antiquated electronics of the room needed a higher voltage for the microphone--nothing dangerous, though.

At this moment, I thought of the cheese, grapes, wine and sodas waiting for us on the 8th floor, the beckoning respite. Was this the moment at which we yield to fate? I should not have underestimated our speaker. "It will be fine," she announced, "if I keep this cable out of the puddle."

It was fine. The talk proceeded to its denoument: we don't really have a plurality of theories of causation; we have no theories at all! As we proceeded to question time, I took the opportunity to apologize publicly for all the hi jinks and to thank her for her forebearance. She responded with a graceful, somewhat bemused smile that let me know that some matters were too important to let the  powers of darkness and electrocution interfere.

John D. Norton

Nancy Cartwright
London School of Economics and University of California at San Diego
24 March 2006
::: Hunting Causes and Using Them
::: Annual Lecture Series