I’ve argued previously, and consistently, that the Universe is not deterministic; however, many if not most physicists believe it is. I’ve even been critical of Einstein for arguing that the Universe is deterministic (as per his famous dice-playing-God statement).
Recently I’ve been watching YouTube videos by theoretical physicist, Sabine Hossenfelder, and I think she’s very good and I highly recommend her. Hossenfelder is quite adamant that the Universe is deterministic, and her video arguing against free will is very compelling and thought-provoking. I say this, because she addresses all the arguments I’ve raised in favour of free will, plus she has supplementary videos to support her arguments.
In fact, Hossenfelder states quite unequivocally towards the end of the video that ‘free will is an illusion’ and, in her own words, ‘needs to go into the rubbish bin’. Her principal argument, which she states right at the start, is that it’s ‘incompatible with the laws of nature’. She contends that the Universe is completely deterministic right from the Big Bang. She argues that everything can be described by differential equations, including gravity and quantum mechanics (QM), which she expounds upon in some detail in another video.
My immediate reaction to this: is what about Poincare and chaos theory? Don’t worry, she addresses that as well. In fact, she has a couple of videos on chaos theory (though one is really about weather and climate change), which I’d recommend.
The standard definition of chaos is that it’s deterministic but unpredictable, which seems to be an oxymoron. As she points out, chaotic phenomena (which includes the weather and the orbits of the planet, among many other things, like evolution) are dependent on the ‘initial conditions’. An infinitesimal change in the initial conditions will result in a different outcome. The word ‘infinitesimal’ is the key here, because you need to work out the initial conditions to an infinite decimal place to get the answer. That’s why it’s not predictable. As to whether it’s deterministic, I think that’s another matter.
To overcome this apparent paradox, I prefer to say it’s indeterminable, which is not contentious. Hossenfelder explains, using a subtly different method, that you can mathematically prove, for any chaotic system, that you can only forecast to a finite time in the future, no matter how detailed your calculation (it’s worth watching her video, just to see this).
Because the above definition for chaos seems to lead to a contradiction or, at best, an oxymoron, I prefer another definition that is more pragmatic and is mostly testable (though not always). Basically, if you rerun a chaotic phenomenon, you’ll get a different outcome. The best known example is tossing a coin. It’s well known in probability theory (in fact it’s an axiom) that the result of the next coin toss is independent of all coin tosses that may have gone before. The reason for this is that coin tosses are chaotic. The same principle applies to throwing dice, and Marcus du Sautoy expounds on the chaos of throwing dice in this video. So, tossing coins and throwing dice are considered ‘random’ events in probability theory, but Hossenfelder contends they are totally deterministic; just unpredictable.
Basically, she’s arguing that just because we can’t calculate the initial conditions, they still happened and therefore everything that arises from them is deterministic. Du Sautoy (whom I referenced above) in the same video and in his book, What We Cannot Know, cites physicist turned theologian, John Polkinghorne, that chaos provides the perfect opportunity for an interventionist God – a point I’ve made myself (though I’m not arguing for an interventionist God). I’m currently reading Troy by Stephen Fry, an erudite rendition based on Homer’s tale, and it revolves around the premise that one’s destiny is largely predetermined by the Gods. The Hindu epic, Mahabharata, also portrays the notion of destiny that can’t be avoided. Leonard Cohen once remarked upon this in an interview, concerning his song, If It Be Your Will. In fact, I contend that you can’t believe in religious prophecy if you don’t believe in a deterministic universe. My non-belief in a deterministic universe is the basis of my argument against prophecy. And my argument against determinism is based on chaos and QM (which I’ll come to shortly).
Of course, one can’t turn back the clock and rerun the Universe, and, as best I can tell, that’s Hossenfelder’s sole argument for a deterministic universe – it can’t be changed and it can’t be predicted. She mentions Laplace’s Demon, who could hypothetically calculate the future of every particle in the Universe. But Laplace’s Demon is no different to the Gods of prophecy – it can do the infinite calculation that we mortals can’t do.
I have to concede that Hossenfelder could be right, based on the idea that the initial conditions obviously exist and we can’t rewind the clock to rerun the Universe. However, tossing coins and throwing dice demonstrate unequivocally that chaotic phenomena only become ‘known’ after the event and give different outcomes when rerun.
So, on that basis, I contend that the future is open and unknowable and indeterminable, which leads me to say, it’s also non-deterministic. It’s a philosophical position based on what I know, but so is Hossenfelder’s, even though she claims otherwise: that her position is not philosophical but scientific.
Of course, Hossenfelder also brings up QM, and explains it is truly random but it’s also time reversible, which can be demonstrated with Schrodinger’s equation. She makes the valid point that the inherent randomness in QM doesn’t save free will. In fact, she says, ‘everything is either determined or random, neither of which are affected by free will’. However, she makes the claim that all the particles in our brain are quantum mechanically time reversible and therefore deterministic. However, I contend that the wave function that allows this time reversibility only exists in the future, which is why it’s never observed (I acknowledge that’s a personal prejudice). On the other hand, many physicists contend that the wave function is a purely mathematical construct that has no basis in reality.
My argument is that it’s only when the wave function ‘collapses’ or ‘decoheres’ that a ‘real’ physical event is observed, which becomes classical physics. Freeman Dyson argued something similar. Like chaotic events, if you were to rerun a quantum phenomenon you’d get a different outcome, which is why one can only deal in probabilities until an ‘observation’ is made. Erwin Schrodinger coined the term ‘statistico-deterministic’ to describe QM, because at a statistical level, quantum phenomena are predictable. He gives the example of radioactive decay, which we can predict holistically very accurately with ‘half-lives’, but you can’t predict the decay of an individual isotope at all. I argue that, both in the case of QM and chaos, you have time asymmetry, which means that if you could hypothetically rewind the clock before the wave function collapse or some initial conditions (whichever the case), you would witness a different outcome.
Hossenfelder sums up her entire thesis with the following statement:
...how ever you want to define the word [free will], we still cannot select among several possible different futures. This idea makes absolutely no sense if you know anything about physics.
Well, I know enough about physics to challenge her inference that there are no ‘possible different futures’. Hossenfelder, herself, knows that alternative futures are built-into QM, which is why the multiple worlds interpretation is so popular. And some adherents of the Copenhagen interpretation claim that you do get to ‘choose’ (though I don’t). If the wave function describes the future, it can have a multitude of future paths, only one of which becomes reality in the past. This derives logically from Dyson’s interpretation of QED.
Of course, none of this provides an argument for free will, even if the Universe is not deterministic.
Hossenfelder argues that the brain’s software (her term) runs calculations that determine our decisions, while giving the delusion of free will. I thought this was her best argument:
Your brain is running a calculation, and while it is going on you do not know the outcome of that calculation. So the impression of free will comes from our ‘awareness’ that we think about what we do, along with our inability to predict the result of what we are thinking.
You cannot separate the idea of free will from the experience of consciousness. In another video, Hossenfelder expresses scepticism at all the mathematical attempts to describe or explain consciousness. I’ve argued previously that if we didn’t all experience consciousness, science would tell us that it is an illusion just like free will is. That’s because science can’t explain the experience of consciousness any better than it can explain the intuitive sense of free will that most of us take for granted.
Leaving aside the use of the words, ‘calculation’ and ‘software’, which allude to the human brain being a computer, she’s right that much of our thinking occurs subconsciously. All artists are aware of this. As a storyteller, I know that the characters and their interactions I render on the page (or on a computer screen) largely come from my subconscious. But everyone experiences this in dreams. Do you think you have free will in a dream? In a so-called ‘lucid dream’, I’d say, yes.
I would like to drop the term, free will, along with all its pseudo-ontological baggage, and adopt another term, ‘agency’. Because it’s agency that we all believe we have, wherever it springs from. We all like to believe we can change our situation or exert some control over it, and I’d call that agency. And it requires a conscious effort – an ability to turn a thought into an action. In fact, I’d say it’s a psychological necessity: without a sense of agency, we might as well be automatons.
I will finish with an account of free will in extremis, as told by London bomber survivor, Gill Hicks. Gill Hicks was only one person removed from the bomber in one of the buses, and she lost both her legs. As she tells it, she heard a voice, like we do in a dream, and it was a female voice and it was ‘Death’ and it beckoned to her and it was very inviting; it was not tinged with fear at all. And then she heard another voice, which was male and it was ‘Life’, and it told her that if she chose to live she had a destiny to fulfil. So she had a choice, which is exactly how we define free will and she consciously chose Life. As it turned out, she lost 70% of her blood and she had a hole in the back of her head from a set of keys. In the ambulance, she later learned that she was showing no signs of life – no pulse and she had flatlined – yet she was talking. The ambo told the driver, ‘Dead but talking.’ It was only because she was talking that he continued to attempt to save her life.
Now, I’m often sceptical about accounts of ‘near-death experiences’, because they often come across as contrived and preachy. But Gill Hicks comes across as very authentic; down-to-Earth, as we say in Oz. So I believe that what she recalled is what she experienced. I tell her story, because it represents exactly what Hossenfelder claims about free will: it defies a scientific explanation.
No comments:
Post a Comment