Pusey and all that jazz
December 7, 2013 3 Comments
In this post I’m going to present some philosophical dialogues to help explain what’s wrong with some current debates about quantum mechanics.
Philosophical Dialogue 1: The Right Argument
Scene: the living room of John’s house, where John is sitting at his computer. Jane enters.
Jane: This house does not exist.
John looks around, he seems appropriately puzzled.
John: Why do you say that?
Jane: I admit that the idea that this house exists can be used to do calculations of things like air currents, but it doesn’t actually exist, it’s just a rule for computing temperature and air currents.
John: That’s dumb. All you’re doing is taking the idea that the house does exist relabelling part of it as not existing. What you’re saying just makes the explanation of the air currents and temperature more complicated and less clear.
Jane: Oh, this metaphysical fantasy that the house actually exists is just complete hogwash, it’s not the sort of thing with which I, as a practical person, can possibly be expected to believe.
John: Your incredulity is not an argument. Kindly go away you silly person.
Philosophical Dialogue 2: The Wrong Argument
Scene: the living room of John’s house, where John is sitting at his computer. Jane enters.
Jane: This house does not exist.
John looks around, he seems appropriately puzzled.
John: Why do you say that?
Jane: I admit that the idea that this house exists can be used to do calculations of things like air currents, but it doesn’t actually exist, it’s just a rule for computing temperature and air currents.
John: But when I do experiments I find that the house does exist.
Jane: No you don’t. You just find that the air currents and temperature can be predicted with the house formulae, which are just tools for calculation.
John: Oh yeah. Well, I’ll prove it by coming up with a great experiment to test your idea. An experiment that will trash your idea forever.
Jane: So what?
Commentary
The statistical interpretation of quantum mechanics is the idea that quantum mechanics is just a set of formulae for calculating probability. The appropriate response to this is to say something similar to what John said in the first dialogue. A few years ago, Pusey et al proposed an experiment that they claimed would test the statistical interpretation of quantum mechanics. This is analogous to what John said in the second dialogue. Pusey et al are wrong, not because the statistical interpretation is right but because they give it too much credit. The statistical interpretation is complete garbage and cannot be tested by any conceivable experiment because it says nothing about anything. The statistical interpretation may or may not lead people into making some mistakes when doing calculations, but it is mistaken about physics and epistemology.
Physics is about what exists in reality. It is not about formulae for calculating stuff. The formulae are useful for testing ideas about what exists in reality and they may also have technological applications. But in both applications it is important to keep your eye on the underlying physical reality so you understand what you’re doing with the formulae. If you don’t keep your eyes on the prize you will end up making epistemological and technological mistakes.
To understand better what quantum mechanics says about reality read the structure of the multiverse, The Fabric of Reality and The Beginning of Infinity by David Deutsch.