24 October 2008
War Games and Blood Shed

We were assembling the October calendar just as I returned from a visit to the Perimeter Institute, where I'd given a talk at a conference. There was still space, Joyce mentioned. So I asked her to put my name down. That same talk would fill the space nicely. It was only later that the nagging sense of disquiet appeared and I began to ask myself, "Do I really want to give this talk?"

My talk is standard fare in philosophy of science, so you would think it could be no cause for anxiety. How do space and time get into our physical theories? Are they posited ab initio as a fundamental component of our ontology, much as an atomist begins with the positing of atoms. Or do space and time enter at a later stage as properties of thing that are more fundamental. Then their status would be closer to that of colors, say, for an atomist. For colors only enter once we have posited atoms and assembled them to provide surfaces that might reflect just the red frequencies of light.

The debate is age old. Its latest iteration comes with Harvey Brown's recent book Physical Relativity: Space-time Structure from a Dynamical Perspective, in which he advocates a secondary position for space and time. The immediate inspiration comes from the great Dutch physicist and ether theorist, Henrik Antoon Lorentz. He was Einstein's precedessor and he found that now familiar relativistic effects, such at the slowing of rapidly moving clocks and shrinking of rapidly moving rods, could be inferred from the electrodynamical properties of matter.

Harvey has no interest in bringing back the ether. But he does think that Lorentz got one part right. Effects customarily conceived as arising from the structure of space and time are actually properties of matter. Moving rods do not shrink because of a property of space and time; they shrink because of a property of matter.

Explanation has been central to the ensuing debate. My colleague and friend Michel Janssen urges that Harvey is wrong: spacetime structure explains why the rods contract. No, Harvey replies, the properties of the matter of the rods explain why spacetime has the structure it has. You might expect such a starkly defined difference to lend itself to rapid resolution. Alas, that is not the case. The trouble is that our accounts of explanation are sufficiently incomplete as not to support clear decisions in these cases. Whether this explains that often comes to personal, even ineffable judgments. It just feels right. What do we do when two able philosophers have diametrically opposed feelings?

That is where the artistry of philosophy of science enters. It is like a chess game. When black and white are locked in intractable struggle, the winning player may suddenly see an unanticipated avenue of attack. I had been pondering this debate and I saw the game changer while walking home one day on Smithfield Street in downtown Pittsburgh. Constructivist, such as Harvey Brown, merely presume that one can construct the full spacetime structure from the properties of matter. I now saw that this was not so. Indeed the construction can only succeed in so far as the constructivists explicitly or tacitly presume exactly the list of commitments that comprise realism about spacetime.

That small point was my talk today. Dan Parker had performed the service of introducing me, ably. I stood at the front of the room with the talk's title on the screen behind me. Looking out over the assembled faces, I could see that they had come for the chess match, the wargame. I expected that I would satisfy them, one way or another. I had my argument sketched out in Powerpoint slides with carefully drawn images of "red" spacetimes and "green" spacetimes.

Perhaps they would relish the ingenuity of the core argument and be swayed by the confidence I would try to project in the presentation.

Or perhaps they would take it all as an invitation to open a new chess game in question time. An innocent "I didn't quite understand what you meant by..." would really be a feint, trying to hide a lightning, backdoor checkmate. Standing there as the talk is about to begin, I do not know if that attack will come or if it will succeed.

This is the academic game, a refined wargame in which armies rise and fall, innocents are slaughtered and no drop of real blood is ever shed. It's all good fun.

Well, it isn't. Behind the game is real war in which blood is shed and people are hurt. And that is why I am feeling anxious today. We philosophers of science are passionate about our work. Harvey has worked for years, distilling his insights and late nights into pages of text. How he and all of us yearn for that affirmation. "Yes, you've done it. That settles it."

It is one thing to stand and play performance chess before this group in Pittsburgh, an ocean away from Harvey's office in Oxford. It is another to stand before an audience in which Harvey sits.

That was the Perimeter Institute. As I spoke to its steeply raked tiers, I was acutely aware of just one face sitting on the left closer to the back, well above the height of my head. There was Harvey, who had spent the previous year as a visitor at the Perimeter Institute. He has been a friend for over 20 years and I know that he is wishing I would make a quite different kind of speech. And here was I getting on with the business at hand.

What else could I do? These are core questions of philosophy of space and time. Every one of us in the field must form our views. We can answer to one master only. It is that inner whisper that guides us through the thicket of thesis and counter-thesis, that warns us of seductive fallacies and prompts us to spend a little more time with that new thought.

Harvey 's was the first question. "I'll meet you round the back afterwards!" he quipped. And afterwards he caught my eye and said "Dinner?" It was the high point of the conference for me.

Now, as I began to speak in Pittsburgh I said, "What I want to do is give you my side of a debate I am having with Harvey Brown. I have to say that I like Harvey and count him as a friend..." My audience dismisses this as a perfunctory display. I cannot say any more or they will grow impatient, waiting for pawn to king four.

John D. Norton

John D. Norton
::: Why Constructive Relativity Fails
Friday, 24 October 2008
12:05 pm, 817R Cathedral of Learning