You Don't Have Free Will, but Don't Worry?

I haven’t watched the whole video, but I’ve read her making similar remarks before. I think she is just referring to the success of modern physics in general. It is a classic reductionist statement, as is evident here (emphases mine):

These deterministic laws of nature apply to you and your brain because you are made of particles, and what happens with you is a consequence of what happens with those particles. A lot of people seem to think this is a philosophical position. They call it “materialism” or “reductionism” and think that giving it a name that ends on –ism is an excuse to not believe it. Well, of course you can insist to just not believe reductionism is correct. But this is denying scientific evidence. We do not guess, we know that brains are made of particles. And we do not guess, we know, that we can derive from the laws for the constituents what the whole object does. If you make a claim to the contrary, you are contradicting well-established science. I can’t prevent you from denying scientific evidence, but I can tell you that this way you will never understand how the universe really works.

Of course, even if one is a reductionist, anyone who has read even a little bit on the philosophy of science on reductionism would see that the above statement is incredibly simplistic and naive. Non-reductionists are not simply “denying scientific evidence”. Rather there is a debate on the precise philosophical implications of the scientific evidence.

And of course there has also been a centuries-long debate on what free will is, as we’ve seen in this and related threads. I skimmed through Sabine’s blog post and I am not very interested to engage about it, since it doesn’t seem to be aware of the deep philosophical literature on the subject. It reminds me of 2000s-era, anti-intellectual New Atheism which ran roughshod over centuries of careful philosophical debate by claiming “science” and “Courtier’s reply”.

You can also see one of her posts last week where Sabine talks about these laws of physics (Sabine Hossenfelder: Backreaction: What are Differential Equations and how do they work?). As you can see she doesn’t really invoke any particular experiment or discovery, just the general success of physics in predicting natural phenomena and using that to make a literally Laplacian argument for determinism. Honestly, even past discussions on determinism and physics on this forum (including several trained physicists) have been more illuminating and interesting: Predictability Problems in Physics.


I took it as a general reference to physics.

And I disagree with that. What I choose to eat today will affect which particles are part of my body tomorrow. Her account is too simplified. If you want to use particle physics for this, it cannot be just the particle physics of one person’s body. You have to include the particles that the person might ingest, breath, etc.

It seems to me this is implicitly understood. The brain and body behaves the way it does given some environment with which it interacts.

I also think, to the extend that anybody doubts this is true and demand some sort of experiment to show it, they can only hide their skepticism in the degree of complexity of the problem. The fact that we cannot really accurately simulate an entire human body and brain in a realistic environment due to limitations of computer processing and memory, and therefore can’t really predict human behavior all that well, is the last gap into which all sorts of absolute bs is now hiding. But it’s fundamentally no different from simply scaling up a “billiards table” problem to a point where it takes too long to compute how it behaves. You’re welcome to convince yourself the scale of the problem implies physics doesn’t explain how the balls will roll around just because, if there are enough balls on the table, no extant computer has the memory and processing power required to simulate the game.

I just can’t wrap my head around how some people haven’t caught on yet, and think that there’s still room for hope that carbon atoms stop behaving like carbon atoms once they’ve found their way into tissues in their brain. It’s ridiculous.

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This is another example of a typical naive view of the problem with little awareness of the professional philosophical literature on the problem of reductionism (which is btw not necessarily tied to Christianity or religious apologetics at all). As philosopher Nancy Cartwright has argued pretty strongly (“Fundamentalism vs. the Patchwork of Laws”), it is a form of begging the question in favor of reductionism and “physics fundamentalism”. In short, the problem with this example is that we don’t know that the human body is nothing more than a bunch of billiard balls bumping together via Newtonian mechanics, and there is no experimental demonstration that this is the case, unless you simply assume a reductionist viewpoint that “because I can model the behavior of a few electrons, and the human body must have some electrons in it, thus I can fully deterministically model the behavior of the entire human body like I can with electrons.”

Yes, physicists are able to predict the behavior of a few particles pretty well. (Although, as anyone who’s familiar with even a bit of quantum chemistry knows, once you get away from the hydrogen atom things get super complicated very quickly and one must rely heavily on experimental data.) But unless you’re begging the question, that doesn’t say much about our ability to exhaustively, deterministically model larger complex systems. There’s even a case to be made that reductionism doesn’t always work in the case of diatomic molecules; there are some features of the molecules that have to be inputted by hand, based on experimental data. Finally, as some biologists argued to me just a few days ago (Some basic questions about genetic variation), the bottom-up, physics-based deterministic approach is actually discouraged when we’re trying to understand a biological cell. One simply can’t gain much insight into the behavior of biological cells by looking at the collective behavior of carbon atoms. Instead one has to look at the cells themselves. This is why the idea of “emergence” is a thing among many biologists and philosophers.

Please don’t misunderstand what I’m saying: I agree that if one can model the behavior of 10 billiard balls, then there’s good reason to expect that we can model 100 billiard balls using the same methods but just more computational power (i.e. drudgery). However, we don’t know that the human body is nothing more than a few trillion identical billiard balls obeying a set of simple laws like Newtonian mechanics. There could be (and probably are) other higher-level principles that come into play once you put together different types of “billiard balls” to form something else entirely, like cells and organs. These higher-level principles might not contradict the Newtonian physics of billiard balls, but they also might not be reducible to them. And without a strong philosophical or scientific argument it is not ridiculous to think that there could be some higher-level principles that are not reducible to them.


Underlying any real notion of choice must be thought, underlying thought must be perception, and underlying perception must be stimulus. The stimulus may be fully described in terms of physics, such as a frequency of light which corresponds to some arrangement of billiard balls in our head, but how can the perception itself be described in terms of physics, such as the red paint of a barn?

This may be an emergent phenomena, something which, while not independent, cannot be fully described in terms of the laws which are sufficient to govern the more fundamental reality. Or stated another way, if the universe were sterile but otherwise as it is, in what manner could the color “red” be said to even exist? So the perception is emergent, as is ultimately thought and will. The interesting and I think open question is, what is the nature of emergence and can it exist within the physical world while granting some degree of freedom from determinism? If perception is the universe becoming self aware, is will the universe becoming self determining?