The question that often comes up in the free will debate is whether the universe is deterministic or indeterministic. Regardless of which one, I argue, free will is entirely incompatible. In a deterministic universe we couldn’t have done otherwise, and in an indeterministic universe that would allow for a change in variables that lead to an otherwise, those indeterministic variables wouldn’t have been “of our own accord” or “up to us”. In other words, we couldn’t have, of our own accord, done otherwise.
But this isn’t enough for some people. Some want to insist that the universe is causally deterministic… period… no questions asked. Others insist on the opposite, that the universe is indeterministic (suggesting that determinism has been “disproven”). It seems being agnostic on these just isn’t good enough for a whole lot of people.
So which is it? Is the universe deterministic or is it indeterministic? And if we don’t know, are one of these options more likely than the other? Rather than give you a direct answer (as I am agnostic here), for this post I want to get into some key talking points that I feel are often missed.
To address these questions, the first thing we need to do is clarify what we mean by “determinism” and “indeterminism”. For the free will debate, the term “determinism” simply means that every event in the universe has a cause, and “indeterminism” means that some events (whether that be one or many) do not have a cause – what I will refer to as “acausal events”. To get the specific as to why these are the definitions that are used, please read here:
“Determinism” and “Indeterminism” for the Free Will Debate
There are other ways that these terms can be used, but the link above will explain the one that is most often used in both physics and the free will topic, and why that’s the case.
Once this semantic is clear, we can move on to assessing one over the other. For an indeterministic universe, we are basically saying that some events simply “happen” without a cause. In other words, the event just “pops into existence”. For some this idea is just too much to handle. They can’t imagine something happening without a cause – without a reason for it happening.
They might ask “but why did the acausal event happen”, and that feels like a sensible question. If, however, an event doesn’t have a cause, there is no “why” to answer. A “why” automatically assumes a cause, so the question of “why” is question begging.
The idea of an acausal event is very un-intuitive. Let’s, however, keep in mind that just because something is un-intuitive doesn’t mean that such is “logically impossible”. To show that something is logically impossible one needs to show how it leads to a contradiction of some sort.
Here are some key talking points that I feel need to be addressed. There may be others I’m missing, but these ones are key factors to have a discussion.
Problems with an Indeterministic Universe
Acausal events aren’t logically impossible (or have not been logically ruled out yet), but let’s look at some of the problems they do have by looking at this infographic I made a while back:
As you can see, there are some problems that acausal events have to contend with. For example, the idea that an acausal event can happen “to” something that is already in existence is problematic, as that suggests the thing is causing the acausal event. This is a problem if we are to say that the radioactive decay of an atom happens without a cause. Rather, the acausal event would need to come into existence first and cause the atom to decay. The problem with this is that an acausal event would have no spatial or temporal determinacy. It would have to be by sheer happenstance that it hit the atom to decay it.
The second part, and the part that is probably the most problematic, is that in physics we have some conservation laws that are generally accepted. For example, the conservation of energy. An event that just comes into existence seems like it would be adding “new energy” into the universe, something that would seem to violate conservation laws. There are some possible work-arounds such as a compensation that happens where the new energy is only temporary (since conservation laws address the total amount of the system is conserved over time), but these “work-arounds” don’t seem very compelling.
The other thing we could do is reject conservation laws and say they might not be the case. That even though we have not shown a case where energy wasn’t conserved in the laboratory, it could be the situation that there are infrequent cases in which it’s not conserved at the quantum scale. Or there may be other loopholes we are not aware of yet.
Similar types of inconsistencies may occur with special relativity, in which case there may be unconvincing loopholes, or a rejection of special relativity needed.
It’s important to note that there is no real evidence that an event is acausal, and it would be difficult to show it. To be able to prove such an event we would have to rule out both local-causality (which for some events Bell’s theorem, if we accept it, rule such out) and at the same time rule out the possibility of a non-local event taking place. Given those parameters it’s theoretically possible to “rule in” an acausal event – but currently this has not been done.
Some people suggest that at the quantum scale, rather than acausal events, you have ontic probabilities. This notion, however, I think can be ruled out logically. This post isn’t going to get into that but if you want to know why ontic probability is impossible, read here:
Ontic Probability Doesn’t Exist: Assessing “Probability” for the Free Will Debate
This is problematic for quantum interpretations that postulate quantum probability as ontic (existing) rather than simply epistemic (just a part of our lack of knowledge).
Problems with a Deterministic Universe
Though I think ultimately a deterministic universe is less problematic than in indeterministic universe, that doesn’t mean it is without its own problems.
Correlation does not necessarily imply causation
One problem with causality that has been around since David Hume is the understanding that we never truly observe causes, but rather correlations. We then infer causality through consistent observations of correlation. Even something obvious like a cue ball hitting an eight ball we don’t really see the energy transfer, the particle interaction, and so on. This in no way implies that causality isn’t inferred, it is. It does, however, make it problematic for us to assess causality for all observable relations, especially those that we don’t have or can’t assess consistent correlations for.
Problems for deterministic quantum interpretations
Per quantum mechanics, if we are to accept that the universe is deterministic, we need to postulate something that is unintuitive about certain quantum events. For example, if we accept Bell’s theorem, certain causal variables need to be “non-local hidden variables”. This means that they happen from a distance, rather than our more classical notions of local causality where one event causes another within close proximity. They also need to be “contextual” which has some of its own unintuitive problems when it comes to non-local events. Bohmian mechanics (also known as pilot wave theory) is a popular contextual non-local hidden variable theory.
Non-local hidden variable theories are also problematic for special relativity. Similar to some of the problems with acausal events, there may be unconvincing “loopholes” here, or it might be the case that we need to reject some aspects of special relativity.
There may be some “loophole” theories that allow for local hidden variables, but those have their own uphill battle to contend with in quantum mechanics.
Another deterministic model is to take a realist account of a “many-worlds” interpretation, which postulates an endless number of (real) “universes” or “worlds” that come about (that decohere into each universe). This position itself has its own logical problems to contend with. For example, the idea that what is in superpositioned states are “possibilities”doesn’t make a whole lot of sense. Rather, all of those events would all be the output of the initial cause, each leading to their own specific environment (world). But this isn’t how many-worlds is thought of.
Out of all of the interpretations, the many-worlds interpretation if postulating that these universes actually do exist, is the interpretation that makes one of the more extraordinary claims that aren’t (nor can it be) empirically backed up. This is a falsification problem.
To read more on some of these issues, and also on why the many worlds interpretation is incompatible with free will (and even in ways a fatalistic account), read here:
Did Everything Begin or Not?
One last thing to discuss has less to do with the events within our known universe, and more to do with the start of everything. If we project that there can be no acausal events, we must assume there isn’t really a “beginning of everything”. We must infer an infinite or circular regress, or a static, eventless, everything that always existed. Each of these options have their own unintuitive problems to contend with that cannot be neglected in discourse about the possibility of acausal events. And if we suggest that everything “began” at some point, we are automatically suggesting an event without a cause – giving credence to that as a possibility. These questions seem unanswerable and speculative at best, but that isn’t the point of the exercise of thinking about these things. Rather, the greater point is to show how a wrench can be thrown into our intuitive thoughts and feelings about everything needing a cause or some things not needing a cause, no matter what side we tend to take.
There are some unintuitive implications no matter how we slice it.
Those who say that they know for a fact that the universe is entirely deterministic, I’d suspect, usually do so due to the intuitive nature of classical causality. It just feels like this must be the case. It just seems like something couldn’t happen without an event that pushes it to its reality. And that intuition could very well be correct.
And though, on the surface, this feels intuitive, it isn’t as easy as it seems. Suggesting that every event has a cause has its own problems one needs to contend with, some of which are intuitive as well once they are thought about.
On the other end of the spectrum there are people who claim that determinism has been disproven. This, however, is equally as false, and usually stems from the acceptance of an indeterministic interpretation of quantum mechanics (e.g. Copenhagen interpretation), which tend to be the first interpretation taught or a primary focus in quantum physics (which I find problematic).
There are interpretations of quantum mechanics that are entirely deterministic (albeit they may be non-local, etc.). And those interpretations are not any less valid. In other words, no empirical evidence exists that currently removes an interpretation (and when there is such, an interpretation becomes abandoned). Each theory is consistent with the experiments and observations – pushing us to interpret the theories – moving us closer to philosophy rather than science in regards to which interpretation makes the most sense (something I have my own thoughts about).
If you feel like the question about determinism or indeterminism hasn’t been answered at all in this post, you are absolutely correct. The only thing I wanted to address is some of the “talking points” that one needs to go over to even have a discussion about this. We need to be careful of just making blind assertions about one over the other.
If you just want my opinion, I’m in the camp that there is probably a good chance that the universe is entirely deterministic. I don’t think quantum mechanics rules out (contextual non-local) determinism, and I think some of the so-called “indeterministic” interpretations of quantum mechanics assert a more problematic type of acausality that isn’t really coherent. But quantum interpretations aside, I don’t see acausal events as being logically ruled out, so I cannot know that they are impossible. I cannot take my position as anything strong. In regards to the free will topic this is the reason I insist on Hard Incompatibilism over Hard Determinism, I truly do think we need to show how free will is lacking in both types of universes (and there simply isn’t a third option).
Rather than make hasty conclusions about what universe we live in, let’s look at all of the problems with both, and take all factors into consideration. The moral: though intuitions can be helpful, let’s not be too much of a slave to our own intuitions or preconceptions. There is no need to dogmatically hold firmly to one over the other. Have intuitive leanings, sure…but try not to insist unless you can address each of the points in this post (and probably many I’ve missed – for example, with certain theories of time) and make strong empirical and logical conclusion of one over the other. If you take up such a daunting task – good luck!
*If you want a complete breakdown about causal and acausal events, check out my book on Amazon.