Puzzles for Physicalists

post by jessicata (jessica.liu.taylor) · 2020-03-12T01:37:13.353Z · LW · GW · 15 comments

This is a link post for https://unstableontology.com/2020/03/12/puzzles-for-physicalists/

Contents

  Indexicality
  Pre-reduction references
  Epistemic status of physics
  Anthropics
  Tool use and functionalism
  Causality versus logic
  Conclusion
None
16 comments

The following is a list of puzzles that are hard to answer within a broadly-physicalist, objective paradigm. I believe critical agentialism can answer these better than competing frameworks; indeed, I developed it through contemplation on these puzzles, among others. This post will focus on the questions, though, rather than the answers. (Some of the answers can be found in the linked post)

In a sense what I have done is located "anomalies" relative to standard accounts, and concentrated more attention on these anomalies, attempting to produce a theory that explains them, without ruling out its ability to explain those things the standard account already explains well.

Indexicality

(This section would be philosophical plagiarism if I didn't cite On the Origin of Objects.)

Indexicals are phrases whose interpretation depends on the speaker's standpoint, such as "my phone" or "the dog over there". It is often normal to treat indexicals as a kind of shorthand: "my phone" is shorthand for "the phone belonging to Jessica Taylor", and "the dog over there" is shorthand for "the dog existing at coordinates 37.856570, -122.284176". This expansion allows indexicals to be accounted for within an objective, standpoint-independent frame.

However, even these expanded references aren't universally unique. In a very large universe, there may be a twin Earth which also has a dog at coordinates 37.856570, -122.284176. As computer scientists will find obvious, specifying spacial coordinates requires a number of bits logarithmic in the amount of space addressed. These globally unique identifiers get more and more unwieldy the more space is addressed.

Since we don't expand out references enough to be sure they're globally unique, our use of them couldn't depend on such global uniqueness. An accounting of how we refer to things, therefore, cannot posit any causally-effective standpoint-independent frame that assigns semantics.

Indeed, the trouble of globally unique references can also be seen by studying physics itself. Physical causality is spacially local; a particle affects nearby particles, and there's a speed-of-light limitation. For spacial references to be effective (e.g. to connect to observation and action), they have to themselves "move through" local space-and-time.

This is a bit like the problem of having a computer refer to itself. A computer may address computers by IP address. The IP address "127.0.0.1" always refers to this computer. These references can be resolved even without an Internet connection. It would be totally unnecessary and unwieldy for a computer to refer to itself (e.g. for the purpose of accessing files) through a globally-unique IP address, resolved through Internet routing.

Studying enough examples like these (real and hypothetical) leads to the conclusion that indexicality (and more specifically, deixis) are fundamental, and that even spacial references that appear to be globally unique are resolved deictically.

How does this relate to physics? It means references to "the objective world" or "the physical world" must also be resolved indexically, from some standpoint. Paying attention to how these references are resolved is critical.

The experimental results you see are the ones in front of you. You can't see experimental results that don't, through spacio-temporal information flows, make it to you. Thus, references to the physical which go through discussing "the thing causing experimental predictions" or "the things experiments failed to falsify" are resolved in a standpoint-dependent way.

It could be argued that physical law is standpoint-independent, because it is, symmetrically, true at each point in space-time. However, this excludes virtual standpoints (e.g. existing in a computer simulation), and additionally, this only means the laws are standpoint-independent, not the contents of the world, the things described by the laws.

Pre-reduction references

(For previous work, see "Reductive Refrerence" [LW · GW].)

Indexicality by itself undermines view-from-nowhere mythology, but perhaps not physicalism itself. What presents a greater challenge for physicalism is the problem of pre-reduced references (which are themselves deictic).

Let's go back to the twin Earth thought experiment. Suppose we are in pre-chemistry times. We still know about water. We know water through our interactions with it. Later, chemistry will find that water has a particular chemical formula.

In pre-chemistry times, it cannot be known whether the formula is H2O, XYZ, etc, and these formulae are barely symbolically meaningful. If we discover that water is H2O, we will, after-the-fact, define "water" to mean H2O; if we discover that water is XYZ, we will, after-the-fact, define "water" to mean XYZ.

Looking back, it's clear that "water" has to be H2O, but this couldn't have been clear at the time. Pre-chemistry, "water" doesn't yet have a physical definition; a physical definition is assigned later, which rationalizes previous use of the word "water" into a physicalist paradigm.

A philosophical account of reductionism needs to be able to discuss how this happens. To do this, it needs to be able to discuss the ontological status of entities such as "water" (pre-chemistry) that do not yet have a physical definition. In this intermediate state, the philosophy is talking about two entities, pre-reduced entities and physics, and considering various bridgings between them. So the intermediate state needs to contain entities that are not yet conceptualized physically.

A possible physicalist objection is that, while it may be a provisional truth that water is definitionally the common drinkable liquid found in rivers and so on, it is ultimately true that water is H20, and so physicalism is ultimately true. (This is very similar to the two truths doctrine in Buddhism).

Now, expanding out this account needs to provide an account of the relation between provisional and ultimate truth. Even if such an account could be provided, it would appear that, in our current state, we must accept it as provisionally true that some mental entities (e.g. imagination) do not have physical definitions, since a good-enough account has not yet been provided. And we must have a philosophy that can grapple with this provisional state of affairs, and judge possible bridgings as fitting/unfitting.

Moreover, there has never been a time without provisional definition. So this idea of ultimate truth functions as a sort of utopia, which is either never achieved, or is only achieved after very great advances in philosophy, science, and so on. The journey is, then, more important than the destination, and to even approach the destination, we need an ontology that can describe and usably function within the journeying process; this ontology will contain provisional definitions.

The broader point here is that, even if we have the idea of "ultimate truth", that idea isn't meaningful (in terms of observations, actions, imaginations, etc) to a provisional perspective, unless somehow the provisional perspective can conceptualize the relation between itself and the ultimate truth. And, if the ultimate truth contains all provisional truths (as is true if forgetting is not epistemically normative), the ultimate truth needs to conceptualize this as well.

Epistemic status of physics

Consider the question: "Why should I believe in physics?". The conventional answer is: "Because it predicts experimental results." Someone who can observe these experimental results can, thus, have epistemic justification for belief in physics.

This justificatory chain implies that there are cognitive actors (such as persons or social processes) that can do experiments and see observations. These actors are therefore, in a sense, agents.

A physicalist philosophical paradigm should be able to account for epistemic justifications of physics, else fails to self-ratify. So the paradigm needs to account for observers (and perhaps specifically active observers), who are the ones having epistemic justification for belief in physics.

Believing in observers leads to the typical mind-body problems. Disbelieving in observers fails to self-ratify. (Whenever a physicalist says "an observation is X physical entity", it can be asked why X counts as an observation of the sort that is epistemically compelling; the answer to this question must bridge the mental and the physical, e.g. by saying the brain is where epistemic cognition happens. And saying "you know your observations are the things processed in this brain region because of physics" is circular.)

What mind-body problems? There are plenty.

Anthropics

The anthropic principle states, roughly, that epistemic agents must believe that the universe contains epistemic agents. Else, they would believe themselves not to exist.

The language of physics, on its own, doesn't have the machinery to say what an observer is. Hence, anthropics is a philosophical problem.

The standard way of thinking about anthropics (e.g. SSA/SIA) is to consider the universe from a view-from-nowhere, and then assume that "my" body is in some way sampled "randomly" from this viewed-from-nowhere universe, such that I proceed to get observations (e.g. visual) from this body.

This is already pretty wonky. Indexicality makes the view-from-nowhere problematic. And the idea that "I" am "randomly" placed into a body is a rather strange metaphysics (when and where does this event happen?).

But perhaps the most critical issue is that the physicalist anthropic paradigm assumes it's possible to take a physical description of the universe (e.g. as an equation) and locate observers in it.

There are multiple ways of considering doing so, and perhaps the best is functionalism, which will be discussed later. However, I'll note that a subjectivist paradigm can easily find at least one observer: I'm right here right now.

This requires some explaining. Say you're lost in an amusement park. There are about two ways of thinking about this:

1. You don't know where you are, but you know where the entrance is.
2. You don't know where the entrance is, but you know where you are.

Relatively speaking, 1 is an "objective" (relatively standpoint-independent) answer, and 2 is a "subjective" (relatively standpoint-dependent) answer.

2 has the intuitive advantage that you can point to yourself, but not to the entrance. This is because pointing is deictic.

Even while being lost, you can still find your way around locally. You might know where the Ferris wheel is, or the food stand, or your backpack. And so you can make a local map, which has not been placed relative to the entrance. This map is usable despite its disconnection from a global reference frame.

Anthropics seems to be saying something similar to (1). The idea is that I, initially, don't know "where I am" in the universe. But, the deictic critique applies to anthropics as it applies to the amusement park case. I know where I am, I'm right here. I know where the Earth is, it's under me. And so on.

This way of locating (at least one) observer works independent of ability to pick out observers given a physical description of the universe. Rather than finding myself relative to physics, I find physics relative to me.

Of course, the subjectivist framework has its own problems, such as difficulty finding other observers. So there is a puzzle here.

Tool use and functionalism

Functionalism is perhaps the current best answer as to how to locate observers in physics. Before discussing functionalism, though, I'll discuss tools.

What's a hammer? It's a thing you can swing to apply lots of force to something at once. Hammers can be made of many physical materials, such as stone, iron, or wood. It's about the function, not the substance.

The definition I gave refers to a "you" who can swing the hammer. Who is the "you"? Well, that's standpoint-dependent. Someone without arms can't use a conventional hammer to apply lots of force. The definition relativizes to the potential user. (Yes, a person without arms may say conventional hammers are hammers due to social convention, but this social convention is there because conventional hammers work for most people, so it still relativizes to a population.)

Let's talk about functionalism now. Functionalism is based on the idea of multiple realizability: that a mind can be implemented on many different substrates. A mind is defined by its functions rather than its substrate. This idea is very familiar to computer programmers, who can hide implementation details behind an interface, and don't need to care about hardware architecture for the most part.

This brings us back to tools. The definition I gave of "hammer" is an interface: it says how it can be used (and what effects it should create upon being used).

What sort of functions does a mind have? Observation, prediction, planning, modeling, acting, and so on. Now, the million-dollar question: Who is (actually or potentially) using it for these functions?

There are about three different answers to this:

1. The mind itself. I use my mind for functions including planning and observation. It functions as a mind as long as I can use it this way.
2. Someone or something else. A corporation, a boss, a customer, the government. Someone or something who wants to use another mind for some purpose.
3. It's objective. Things have functions or not independent of the standpoint.

I'll note that 1 and 2 are both standpoint-dependent, thus subjectivist. They can't be used to locate minds in physics; there would have to be some starting point, of having someone/something intending to use a mind for something.

3 is interesting. However, we now have a disanalogy from the hammer case, where we could identify some potential user. It's also rather theological, in saying the world has an observer-independent telos. I find the theological implications of functionalism to be quite interesting and even inspiring, but that still doesn't help physicalism, because physicalist ontology doesn't contain standpoint-independent telos. We could, perhaps, say that physicalism plus theism yields objective functionalism. And this requires adding a component beyond the physical equation of the universe, if we wish to find observers in it.

Causality versus logic

Causality contains the idea that things "could" go one way or another. Else, causal claims reduce to claims about state; there wouldn't be a difference between "if X, then Y" and "X causes Y".

Pearlian causality makes this explicit; causal relations are defined in terms of interventions, which come from outside the causal network itself.

The ontology of physics itself is causal. It is asserted, not just that some state will definitely follow some previous state, but that there are dynamics that push previous states to new states, in a necessary way. (This is clear in the case of dynamical systems)

Indeed, since experiments may be thought of as interventions, it is entirely sensible that a physical theory that predicts the results of these interventions must be causal.

These "coulds" have a difficult status in relation to logic. Someone who already knows the initial state of a system can logically deduce its eventual state. To them, there is inevitability, and no logically possible alternative.

It appears that, while "could"s exist from the standpoint of an experimenter, they do not exist from the standpoint of someone capable of predicting the experimenter, such as Laplace's demon.

This is not much of a problem if we've already accepted fundamental deixis and rejected the view-from-nowhere. But it is a problem for those who haven't.

Trying to derive decision-theoretic causality from physical causality results in causal decision theory, which is known to have a number of bugs, due to its reliance on hypothetical extra-physical interventions.

An alternative is to try to develop a theory of "logical causality", by which some logical facts (such as "the output of my decision process", assuming you know your source code) can cause others. However, this is oxymoronic, because logic does not contain the affordance for intervention. Logic contains the affordance for constructing and checking proofs. It does not contain the affordance for causing 3+4 to equal 8. A sufficiently good reasoner can immediately see that "3+4=8" runs into contradiction; there is no way to construct a possible world in which 3+4=8.

Hence, it is hard to say that "coulds" exist in a standpoint-independent way. We may, then, accept standpoint-dependence of causation (as I do), or reject causation entirely.

Conclusion

My claim isn't that physicalism is false, or that there don't exist physicalist answers to these puzzles. My claim, rather, is that these puzzles are at least somewhat difficult, and that sufficient contemplation on them will destabilize many forms of physicalism. The current way I answer these puzzles is through a critical agential framework, but other ways of answering them are possible as well.

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