Agency and quantum computing

Agency and quantum computing

There are several threads to this post, which I will link together at the end.

First, the ‘hard problem’ of consciousness, according to David Chalmers, is subjectivity, or subjective experience – i.e., there is something it is like to be me – and all current explanations of information processing leave that unexplained. Quantum mechanics leaves an odd gap in the physicalist project, in that it apparently requires causally nonlocal and/or nondeterministic information processing in order to fully explain quantum phenomena, a problem which goes under several names, including ‘the collapse of the wave function.’

An illustrative quote from Chalmers, from his “Facing Up to the Problem of Consciousness”:

“Perhaps the most popular "extra ingredient" of all is quantum mechanics (e.g. Hameroff 1994). The attractiveness of quantum theories of consciousness may stem from a Law of Minimization of Mystery: consciousness is mysterious and quantum mechanics is mysterious, so maybe the two mysteries have a common source. Nevertheless, quantum theories of consciousness suffer from the same difficulties as neural or computational theories. Quantum phenomena have some remarkable functional properties, such as nondeterminism and nonlocality. It is natural to speculate that these properties may play some role in the explanation of cognitive functions, such as random choice and the integration of information, and this hypothesis cannot be ruled out a priori. But when it comes to the explanation of experience, quantum processes are in the same boat as any other. The question of why these processes should give rise to experience is entirely unanswered.

(One special attraction of quantum theories is the fact that on some interpretations of quantum mechanics, consciousness plays an active role in "collapsing" the quantum wave function. Such interpretations are controversial, but in any case they offer no hope of explaining consciousness in terms of quantum processes. Rather, these theories assume the existence of consciousness, and use it in the explanation of quantum processes. At best, these theories tell us something about a physical role that consciousness may play. They tell us nothing about how it arises.)

At the end of the day, the same criticism applies to any purely physical account of consciousness. For any physical process we specify there will be an unanswered question: Why should this process give rise to experience? Given any such process, it is conceptually coherent that it could be instantiated in the absence of experience. It follows that no mere account of the physical process will tell us why experience arises. The emergence of experience goes beyond what can be derived from physical theory.”

…

Next, I turn to David Darling’s argument for reality of parallel universes given the reality of quantum computing. To simplify, Darling asserts that we have already built quantum computers, and computation always requires a substrate - something on which to compute. But quantum computers are nonlocal - they cannot have a causally closed substrate in 4-dimensional space-time. Hence, on Darling’s view, they can only sensibly be said to be computing across multiple parallel 4-dimensional spacetimes - aka ‘parallel universes’.

So quantum computing - which is already being done - proves the existence of parallel universes, Darling asserts. The usual way of interpreting these multiple universes is via Hugh Everett’s ‘Many Worlds Intepretation’ of quantum mechanics. The wave function in quantum mechanics never in fact collapses; instead, every possible probability distribution is actualized in a separate universe: so there’s a universe in which you read this post to the end, another in which you quit reading now, another in which you ceased existing 5 seconds ago, another… and so on. And all are equally real; but you are only aware of this one, because the information carried by the rest of the quantum wave(s) is now invisible to you - the act of observation guarantees it is in another universe.

…

Third, philosophy has a perennial problem of rational free will, or as we often call it, agency – the problem is, what is it? Our concept of it appears clearly incompatible with determinism (despite the valiant but vain efforts of legions of compatibilists) – to have freedom, it cannot be the case that one could not do otherwise. To be an agent is to have at least two logically, physically possible futures open to me right now: one in which I choose to do X, and one in which I do not.

But agency is also incompatible with causal indeterminism – uncaused events are simply not the same as an act due to agency. If my hand begins flopping around for no apparent reason, I do not believe that proves my agency - instead, it makes me call the doctor. To be an agent, I must be in rational control of which of those possible futures comes into existence. There are (at least) two futures, and ‘it is up to me’ which occurs.

So agency must be conceived as a causal power, but not one that is physically determined by antecedent events. So agency, in conception, is a nonphysical causal power in addition to typical physical causal nexus. But exactly what is this mysterious causal power? Does it really exist, or is agency merely a massive, species-wide delusion, borne of our ignorance of the fine-scale causal structure of our brains and bodies and the world?

…

Recall Chalmers’s Law of Minimization of Mystery: consciousness is mysterious and quantum mechanics is mysterious, so maybe the two mysteries have a common source.

Perhaps the collapse of the wave function in QM, as several interpretations insist, is associated with the consciousness of a physical state. Perhaps the solution of the collapse of the wave function has to do with mind/ agency?

But without some further account, this is simply to replace one mystery with another; and an appeal to mystery is no real explanation at all, but simply an admission of ignorance.

But…. what if biology/ minds can access parallel universes in way that standard 4-dimensional physics cannot, in order to do computations or whatever conscious thinking is?

Suppose that Agency is thought of as the rational examination of (deliberation upon) nearby possible worlds/ parallel universes, and then deciding between them in terms of which one to bring about; to make sense of this, we would need a (non-4D-physical) mental causal power of accessing and deciding between parallel universes to determine which one your mind is to be in after one’s choice.

Such an account could make sense of why there is no causal closure of the (4D) physical, but nonetheless there is always causal closure when agency is included.

So on this hypothesis, agency is an ability to access and decide between various counterfactuals, understood as parallel universe(s), in order to single out one to experience.

…

Some Questions: is this additional causal power to access parallel universes only possible for biology? Implication of Darling’s argument – no, computers / electrons/ photons already do it.

Where am I as agent? If separate parallel universes are 4-branes (4D space-time), then an agent must be in at least a 5-brane in order to choose which to experience.

Some Implications: 1. We have some kind of existence beyond our observed 3D physical body in time. 2. Robots with agency are possible, if they can do quantum computing. Such quantum computing will be needed to move from simulated agency to real agency.


Comments welcome.