[dotsam]

I find the idea of computational irreducibility useful for rescuing a type of free will in a fully determined world. Computationally irreducible programs are perfectly deterministic, yet you can't predict the output before you run them, and nor are there any shortcuts to get there before running them for the first time. The program running in our brains for 'free will' can be computationally irreducible in this way. No-one can say with perfect accuracy what we will choose to do in advance, not even us.

For me, this kind of free will is enough, though it is rather deflationary when compared to some kind of godlike non-causal free will. I think that if we search for non-causal free will, we lose any hope of explanation or understanding: presumably if it's non-causal, then anything can happen, for no reason.

[nwiswell]

I don't think this concept is helpful, honestly. If the brain is deterministic, then you would be able to fully simulate it in a regular von Neumann computer, and as a result you'd be able to predict someone's actions and choices with perfect accuracy, which leaves no space for any agency or "ghost in the machine".

[dotsam]

How do you predict what the full simulation will do, before you run it for the first time? If it is computationally irreducible, then you can't predict the outcome - the only way to know what will happen is to run the computation and see what happens. And this computation, this full simulation, is a person with free agency. They are just running on a non-biological computational substrate.

[nwiswell]

How can you have two persons with free agency that always make the same decision?

Or a hundred such persons?

The calculation itself may be irreducible, but what is the implication for consciousness and agency if, midway through the calculation, you fork the process? What about a quarter of the way, or three quarters?

[dotsam]

Then you have n free and conscious agents! And yes, if their simulated environments were identical, then the copies would all make identical decisions (all the copies would still have the same conscious experiences of free will that you and I have).

Whilst this feels unsatisfactory, it is the only way I can see of talking about agency without invoking decision-making processes that disobey the laws of physics, or rely on randomness. And unless a supernatural version of free will appeals, I think this is the best kind of free will available: governed by rules, but nevertheless fundamentally unpredictable. The only other option would be to rely on complete randomness as a basis for decisions, which seems worse.

[nwiswell]

I think philosophically when we talk about non-causal "free will" it is "not scientifically understood", but that's different than "supernatural".

Just because our perception prevents us from predicting outputs from inputs in a way that appears random does not mean that it is just a chaotic system. This is part of the question posed by the original article: does quantum theory provide certain mechanisms that could permit non-deterministic agents to intervene in causal ways that are not predictable? Or would we have to appeal to the supernatural / mystic / divine in order for such a thing to even be possible?

Certain interpretations (e.g., the "Many Worlds" interpretation of QM) are more conducive to this possibility than others.

Generally, "free will" is simply stated as "the freedom to do otherwise". Returning to the "simulated brain" example -- if the computer simulation is faster than the "squishy brain" agent, then it has already predicted the outcome, and the "squishy brain" agent has no "freedom to do otherwise": the outcome is pre-determined.

[dotsam]

> Certain interpretations (e.g., the "Many Worlds" interpretation of QM) are more conducive to this possibility than others.

> Generally, "free will" is simply stated as "the freedom to do otherwise".

In the Many Worlds interpretation, as I understand it, everything that can happen, does happen (as it would in a single universe of infinite extent). So no matter what you choose to do in one universe, the multiverse-wide outcome is predetermined: copies of you always make all choices not forbidden by the laws of physics.

I think this just pushes the problem of determinism out to the multiverse as a whole.

[featuregag]

This interpretation is very interesting to me. Do you know of any other philosophical or scientific research into the relationship between computational complexity / reducibility and free will?

[dotsam]

Stephen Wolfram's discussion of free will in his book A New Kind of Science is the most relevant:

https://www.wolframscience.com/nks/p750--the-phenomenon-of-f...

Daniel Dennett's book Consciousness Explained comes at the problem from a similar angle.