Time Travel and Backwards Causation

Over at Tapped Matthew Yglesias links (tounge-in-cheek) to the SEP’s entry on backwards causation, with some sarcastic suggestions for how Bush’s defence of the war in Iraq might look better if backwards causation were plausible. I don’t want to enter into the politics of this, but there is something odd about the Stanford piece.

As Matt says, in the debate about backwards causation as such, the main defender of the coherence of the view is Michael Dummett. But surely there are many more defenders of this view, namely all the defenders of the coherence of time travel. (Of which, as the SEP also notes, there are quite a few.)

Well, maybe not. Here’s the entry on backwards causation again.

The idea of backward causation should not be confused with that of time travel. These two notions are related to the extent that both agree that it is possible to causally affect the past. The difference, however, is that time travel involves a causal loop whereas backward causation does not. Causal loops for their part can only occur in a universe in which one has closed time-like curves. In contrast, backward causation may take place in a world where there are no such closed time-like curves. In other words, an ordinary system S taking part in time travel would preserve the temporal order of its proper time during its travel, it would keep the same time sense during its entire flight (a watch measuring S’s proper time would keep moving clockwise); but if the same system S were to become involved in a process of backward causation, the order of its proper time would have to reverse in the sense that the time sense of the system would become opposite of what it was before its back-in-time travel (the watch will start to move counter-clockwise). So neither backward causation nor time travel logically entails each other and time travel is distinct from back-in-time travel.

This seems to me mistaken on several fronts. First, time travel does not logically require closed time-like curves. Plenty of time travel defenders (e.g. Lewis) defend the coherence of sci-fi style ‘jumps’ from one time to an earlier time. This is not scientifically plausible, for several reasons, but then neither is backwards causation. (Except, I should add, in quantum cases where backwards causation might explain the Bell inequality.) Second, there’s no reason to say that backwards causation need be a process. Dummett’s original example was the rain dance on Wednesday causing the rain on Tuesday (or something like this – I don’t have the book in front of me). Backwards causation might be event causation, not process causation. Third, we might have backwards causation along one kind of process, even while we have forward causation in others. Imagine a case where some coffee ‘despills’ from the floor to the coffee cup, but all the while cools down as coffee does at room temperature. It doesn’t have its ‘personal’ time reversed, but there is something we’d generally call backwards causation going on. So I don’t really see why these cases should be treated apart, and these debates kept separate.

Scientific Proof that (some) Temporal Parts Exist

Michael Sprague at PhilBio links to this story (quoted in entirity).

It is almost unbelievable, but scientists have apparently say they have discovered a way to bring dead dogs back to life.

Suddenly those awful scenes in horror movies about zombies rising from the dead could soon be a reality.

Scientists at the Safar Centre in Pittsburgh, by using what they call a suspended animation technique, emptied the dead animals’ veins of all blood and then refilled them with ice-cold saline solution to preserve the tissues and organs.

The animals at the time had no heartbeat or brain activity and were classed as being clinically dead.

The team then replaced the saline solution with fresh blood, and electric shocks were used to restart the dogs hearts.

They say the dogs appeared to be unharmed by their suspension and had suffered no brain damage.

The scientists hope in future to use the technique on humans, possibly within a year, and are already in talks with hospitals about trials on trauma patients.

They believe the procedure could save the lives of people who have suffered massive blood loss, such as battlefield casualties or stabbing victims.

Trauma surgeon Dr Howard Champion, says the results are stunning, as these dogs supposedly had complete cardiac standstill for three hours and then recovered to normality.

Actually Michael linked to the Daily Mail version, but I think News-Medical.Net is more reliable. (That is, I have no information whatsoever about News-Medical.Net, so my subjective trust in it is much higher than my trust in the Daily Mail.)

Anyway, on to the philosophy. It seems to me very hard to find a plausible metaphysical view on which the dog does not have one temporal part before dying, and another temporal part after being brought back to life. On van Inwagen’s view, I guess the dog has to go out of existence, and then the very same thing has to come back into existence a few hours later. Or he has to say that a new dog was constructed (born?) with all the appearances of an older dog. Even on more orthodox endurantist views, on which such things as dog corpses exist, we’d have to say somehow that the dog endures over a period in which it is a corpse, before returning to being a dog. This seems logically plausible, but if anything deserves the name ‘crazy metaphysic’. I can’t see a plausible way through here except to say that there is one part of the dog that ends at its death, and another part of the dog that comes into being when it is reanimated.

One could try and say that the dog stayed being a dog all through the process. But that leads to odd results. When we ask “How many dogs are there in the world?” we don’t want dead dogs that might later be reanimated to be included in the count. So I think there’s no hope for the claim that this thing ceases to be a dog for a while. The dog is temporally gappy, and that’s hard to comprehend without temporal parts.

This is all assuming the story is true. It has appeared in several newspapers, but it could all be an amusing hoax. In which case the debate about temporal parts will have to return to the philosophy classroom.

Open Access

From today’s Guardian.

Thousands of British academics in every subject from art history to zoology will soon be required to make their research freely available online, the UK research councils have announced.

I don’t know enough about the details of this to form an opinion, but this looks like a very striking decision.

Postdocs at Sydney

The University of Sydney is advertising ten postdocs, available in any field, and the department there is encouraging philosophers to apply. Anyone whose PhD is from the last 5 years is eligible. There are more details here.

Of course, it’s currently 60 and raining in Sydney, and 90 and sunny in Ithaca, so I don’t know at all why anyone would want to move there 🙂


I’ve been getting flooded all day with spam from IP address, which if you do a traceroute you’ll find is a pharmaceutical site. (I’m not linking to it because that would just be rewarding the spam.) Even after IP banning them, they are still hitting the site around 50 times an hour – you can see what the error log looks like here. I’d recommend banning that address, and if you get hit with any spam report it to Google as abuse.


My RSS feeds from the journals are not perfect, so I sometimes get a backlog all in at once. Today when I checked I found new editions of each of the following

Mind (including articles on two-envelopes and Bayesian epistemology)
Analysis (with too many good articles to mention)
Nous (with an article on fine-tuning)
Philosophy and Phenomenological Research (with a symposium on Ted’s book)
Philosophical Studies (the Bellingham 03 issue)
Proceedings of the Aristotelian Socity (with a big relative truth paper by MacFarlane)
Mind and Language
Pacific Philosophical Quarterly
Linguistics and Philosophy
Midwest Studies in Philosophy

And I’m sure a few more. If I had 48 hours in each day, I might even get through reading some of these.