The Nature of Reality: Is Consciousness All There Is? (Part 2)

This is the second article in a two-part series that explores neuroscientist Donald Hoffman’s theory of conscious realism, in which he denies the existence of the physical world and proposes that consciousness is the fundamental building block of the universe.^[1]The Case Against Reality: Why Evolution Hid the Truth from Our Eyes by Donald Hoffman

My previous article presents Hoffman’s evolutionary game theoretical approach to the problem of perception, and in it I describe and discuss his conclusion that evolution dictates that the world is not as it appears.^[2]Mark, Marion, and Hoffman, Natural selection and veridical perceptions, Journal of Theoretical Biology 266 (2010) 504–515 (pdf)

I recommend reading the previous article first, if you haven’t already.

A Mathematical Formalism for Consciousness

Having established that reality is likely not what it appears, Hoffman’s next step is, in my opinion, the most interesting part of his argument.  In collaboration with mathematician Chetan Prakash, Hoffman and Prakash (hereafter “HP”) have developed a mathematical representation of consciousness ^[3]Hoffman Donald D., Prakash Chetan, “Objects of consciousness”, Frontiers in Psychology vol 5, 2014.

HP compares their approach to what Alan Turing did for computers.  Turing created an abstract mathematical formalism for a computer (a “Turing machine“) via which any computer can in principle be described in written form.  This abstract formalism then allows one to proceed mathematically in the study of computers, proving and disproving theorems related to computation.

In a similar approach, HP have created a mathematical formalism for consciousness by which any conscious entity can be represented abstractly.  With that abstract mathematical formalism in hand, they can then proceed to prove things about consciousness.  Here’s what their formalism for consciousness looks like.

A conscious agent is defined to be something that has perceptions of the world which form its experience of the world, then makes a decision based on those experiences, and then acts on the world.  HP represent this abstractly as (see diagram at left): there is a world, , and perceptions of the world, . Given its perceptions , the conscious agent has an experience, .  Based on its experience, the conscious agent then makes a decision, , and chooses an action, .  The selected action then influences the world by acting with .

Therefore, a conscious agent can be represented as the collection of all of the above (except the world , because it is external to the conscious agent) and written as:

   

That is, we are using abstract mathematical notation to say that a conscious agent is the collection of its perceptions, experiences, decisions, and actions.

What makes this particularly interesting is HP’s next step, in which they show that the world can be replaced by another conscious agent and everything is still self-consistent within their abstract formulation of conscious agents.

This is done by allowing the perceptions of one agent (“agent one”) be the same as the actions of the other agent (“agent two”).  In other words, agent one’s perceptions of the external world are entirely created by (and are identical to) the actions taken by agent two.  And vice versa: agent two’s perceptions of the world are formed by the actions taken by agent one.  In the notation of the above formulation, (the perception of agent one) is identical to (the action of agent two), and (the perception of agent two) is identical to (the action of agent one). This is represented diagrammatically in the figure below.

Here, we’ve created a loop in which two conscious agents mutually provide perceptions for each other via their actions.  Note that in this diagram there is no world, , and this is the crucial point.  We have removed the physical world entirely and replaced it with another conscious agent.

This process could be repeated by adding a third conscious agent.  In this case, the perceptions of one are informed by the actions of both of the other two, and that is the case for all three agents.  The three-dimensional diagram at the right conveys the idea.

The arrows should be labeled (for perceptions), (for decisions), and (for actions), but these have been omitted in the figure to reduce clutter.

Notice each vertex representing an experience has two incoming channels (the actions of the other two agents).  For example, the experiences of agent one, , are informed by the actions of agents two and three, and .  And similarly, the experiences of agent two () and the experiences of agent three () are each affected by the actions of both of the other agents.

Also notice each vertex representing an action has two outgoing channels since each agent’s actions will influence each of the other two agents.  influences and .  Similarly,   and each influence the experiences of the other agents.

Again, note that there is no world in this diagram.  All that exists are conscious agents, informing the experiences of other conscious agents.

This process could be repeated to add a fourth conscious agent.  The fourth agent influences and is in turn influenced by each of the other three agents.  To represent this in a diagram requires a four-dimensional figure, but to write it in mathematical notation is no harder than writing it for three agents.

To summarize, if you are a conscious agent in this network, then your experiences are influenced by the actions of every other conscious agent in the network.  Similarly, your actions have an influence on the experiences of every other conscious agent in the network.

All of this is done without need for a world .

The take home point is that the world need not exist.  The universe could be nothing but a network of conscious agents and this is consistent with Hoffman and Prakash’s mathematical formalism.

Physics from Consciousness

If the universe were made of conscious agents, then those consciousnesses must belong to brains, right?  Hoffman says no, there are no brains.

Conscious agents are the ontological primitives of the universe.  Everything is built on consciousnesses, including atoms and molecules and even space and time.

In his desktop icon analogy (see part one), we see only the desktop, not the underlying workings of the computer.  And atoms, molecules, space, and time are merely icons on the desktop.  There is something deeper underlying all of it.  And HP theorize that the “something deeper” is consciousness itself.  They’re lead to this belief by their mathematical construction above that shows a physical world need not exist and that a universe consisting of only conscious agents would be indistinguishable to us from having a physical external world.

Normally we think of it as happening the other way around: atoms and molecules form brains and those in turn lead to consciousness.  Hoffman wishes to turn this on its head.  So how is it possible for atoms to be constructed from consciousness?

With their mathematical formalism of conscious agents in hand, HP can proceed with showing (mathematically, at least) how physical entities can arise from networks of conscious agents.  They do this in a very abstract form, showing that quantum mechanical wave functions can be formulated from networks of conscious agents.

HP are unable to say much regarding relativity and spacetime, however.  Constructing spacetime from networks of conscious agents is a proof they leave for future work. ^[7]Hoffman Donald D., Prakash Chetan, “Objects of consciousness”, Frontiers in Psychology vol 5, 2014

The quantum measurement problem

Since Hoffman frequently refers to quantum physics when discussing his theory of conscious realism, let’s have a brief talk about quantum physics.

In quantum physics, objects exist in a “superposition” (i.e., a collection) of states.  Objects exist in such an indefinite state (which is actually a collection of states) until they are measured.  Once measured, the object’s state “collapses” to one definite state out of the collection of states.

How exactly does this “collapse” happen?  What constitutes a “measurement”?  This has been labeled the quantum measurement problem.  Several interpretations of quantum physics have been developed in the last century that propose answers to this problem.  The original interpretation, called the Copenhagen interpretation, is essentially what I described in the preceding paragraph: an object exists in a collection of states until it is measured, and the measurement forces the object’s state to collapse to a single definite state.

The most famous thought experiment illustrating the weirdness of the Copenhagen interpretation is Schrodinger’s Cat. A cat is inside a box.  Also inside the box is a quantum process, such as a radioactive isotope that decays and triggers a poisonous gas (the details of the mechanism aren’t important).  The quantum process in the box either kills or doesn’t kill the cat.  Until we open the box and observe what’s inside, the inside of the box exists in a superposition of both states: the cat is both dead and alive at the same time.  When we open the box (and thereby make a “measurement”), we find that the cat is either one or the other; it’s either dead or alive, but not both.  But until the measurement is made, the cat is in a superposition of being alive and dead at the same time.

I get the sense in listening to his interviews and reading his articles that Hoffman’s conscious realism is partly inspired by the debate over how to interpret quantum physics.  One interpretation, called the Von Neumann-Wigner interpretation, says that the measurement that collapses the quantum object into a definite state doesn’t count as a “measurement” unless it is made by a conscious agent.  For instance, a measurement by an unconscious robot would not cause the object to collapse to a single definite state.  This idea was proposed by Von Neumann in the 1930’s and further investigated by Wigner in the 1960’s.  However, most physicists today do not subscribe to this interpretation of quantum physics.  Indeed, many physicists no longer subscribe to the Copenhagen interpretation either, preferring instead the many-worlds interpretation.

In his interview with Quanta magazine, Hoffman states “Physics tells us that there are no public physical objects.”^[8]The Evolutionary Argument Against Reality, Quanta Magazine, April 21, 2016  Here he means that, since an object exists in a superposition of states until it is measured, the object doesn’t exist at all.  This is a misstatement of the quantum measurement problem.  Saying that something exists in an indefinite state or collection of states is different than saying something is unreal or doesn’t exist at all.

He goes on to say “Quantum mechanics says that classical objects — including brains — don’t exist.” ^[9]The Evolutionary Argument Against Reality, Quanta Magazine, April 21, 2016 (Here, a “classical” object simply means a macroscopic object that behaves like the everyday objects we are familiar with.)  I don’t agree with this, either.  I think a better interpretation is that classical objects are the macroscopic manifestation of quantum objects.  If quantum objects are real, then so are classical ones.

Physics says that classical objects, like brains, do exist.  So while Hoffman purports that modern physics supports his claim that physical objects are unreal, I disagree that modern physics offers any such support.

Spacetime is doomed

Another phrase Hoffman likes to use in his interviews is a quote he’s borrowed from the Institute of Advanced Study’s well-known physicist Nima Arkani-Hamed.  Arkani-Hamed has said “spacetime is doomed” ^[10]The Doom of Spacetime: Why it Must Dissolve into Fundamental Structures, public science talk by Nima Arkani-Hamed.  By this, he means that there is something fundamental missing in our current understanding of spacetime, and eventually we will have to rewrite our understanding (i.e., with the development of a quantum theory of gravity).

When he says “spacetime is doomed”, Arkani-Hamed is saying that spacetime is an emergent property of a deeper reality that we haven’t yet uncovered.  That doesn’t mean, as Hoffman wants to interpret it, that spacetime is unreal.

Hoffman’s conscious realism also posits that spacetime could be an emergent property of something else (in his case, the “something else” is conscious agents).  Most theoretical physicists would likely agree that a deeper reality exists that we haven’t yet discovered.  But, most physicists would likely not suppose that deeper reality to be a network of conscious agents.

Summary of My Thoughts

I’ve offered my analysis in numerous places along the way, but here I will summarize my overall thoughts on Hoffman’s conscious realism.

In Part 1 of this two-part series, I described the evolutionary game that Hoffman, et. al. used to conclude that an accurate perception of the world is driven to extinction by a simple but cost-effective perception.  As I mentioned in Part 1, I think a major hole in their argument is that, as they point out themselves, “Our simulations do not find that natural selection always drives truth to extinction. They show instead that natural selection can drive truth to extinction.” ^[11]Mark, Marion, and Hoffman, Natural selection and veridical perceptions, Journal of Theoretical Biology 266 (2010) 504–515 (pdf) (emphasis theirs)

Even if a truth strategy is driven to extinction most of the time, this is different than always.  Therefore, I feel it is an overly strong conclusion to draw from their computational result that evolution predicts that our perception of reality must be inaccurate.

In Hoffman and Prakash’s paper, they state “…natural selection does not favor perceptual systems that see the truth in whole or in part.”^[12]Hoffman Donald D., Prakash Chetan, “Objects of consciousness”, Frontiers in Psychology vol 5, 2014  This conclusion is also too strong.  Even the simple strategy in the evolutionary game sees truth in part, since it is able to see that some territories have more food than others.

To say that natural selection does not favor perceptual systems that see truth even in part is to disagree with the premise and conclusion of their evolutionary game, in which a strategy that sees truth in part is able to succeed versus a strategy that sees truth in whole.

In Part 2 of this two-part series, I’ve just described Hoffman’s argument that the world need not exist and could, in principle, be replaced by a network of conscious agents that would be indistinguishable from a physical world.

To support his theory that the physical world is unreal, Hoffman wishes to draw upon modern physics — in particular the quantum measurement problem and Nima Arkani-Hamed’s assertion that “spacetime is doomed”.  However, I don’t believe either statement from modern physics offers any such support, for the reasons I’ve stated above.

The idea that the physical world might not exist reminds me of the simulation hypothesis, which supposes that our external world is actually a computer simulation.  This idea has been portrayed in numerous science fiction stories, including The Matrix movie franchise among many others.  Similar scenarios include Descartes’ evil demon (a malevolent and all-powerful entity that deceives his every perception and thought) and the “brain in a vat” hypothesis (in which you are a disembodied brain in a vat, connected by electrodes to a machine that provides all the inputs and outputs to your brain that simulate an external world).

Are we living in a simulated reality?  Are you just a brain in a vat?  If so, how would you prove such a thing?  Better yet, how would you disprove such a thing?

Short of “waking up” and seeing reality as it really is (as Neo does in The Matrix), there really is no way to prove or disprove the simulation hypothesis ^[13]Well, some physicists have tried, nevertheless, to propose physical observations that, if observed, would suggest we’re living in a simulation.  It’s a fascinating idea and perhaps … Continue reading because there is no way to perform an experiment that escapes the fact that the experiment, too, is part of the simulated reality.

Similarly, Hoffman’s theory of conscious realism can be neither refuted nor proven.  If, instead of an external physical world, the universe is made of a network of conscious agents, how could we perform an experiment to verify or falsify such a thing?  Any experiment that you could propose will itself be part of the network of conscious agents which is indistinguishable from an external physical world.

Until Hoffman provides testable predictions, his theory of conscious realism is on the same nonscientific footing as the simulation theory.

That said, the evolutionary game theoretic and mathematical formalism for consciousness arguments that Hoffman uses to arrive at his conclusion are fascinating on their own and worth the consideration and study that’s been devoted to them, in these articles and elsewhere.

Further Information

In 2015, Hoffman gave a short TED talk about his theory of conscious realism (runtime: 21m)

Video interviews:

• Michael Shermer interview on Science Salon (runtime: 1h 45m)
• ZDoggMD interview “What if We’re Wrong About Reality?” (runtime: 1h 50m)
• TED interview (runtime: 55m)

Book reviews of The Case Against Reality: Why Evolution Hid the Truth from Our Eyes:

• Physics World
• Popular Science Books
• LA Review of Books
• Inquisitive Biologist

Hoffman’s peer-reviewed technical articles:

• Mark, Marion, and Hoffman, “Natural selection and veridical perceptions”, Journal of Theoretical Biology 266 (2010) 504–515 (pdf)
• Hoffman Donald D., Prakash Chetan, “Objects of consciousness”, Frontiers in Psychology vol 5, 2014

In-depth Critiques:

• Philosopher Jonathan Cohen’s critique in Psychonomic Bulletin and Review
• “Hoffman’s Conscious Realism: A Critical Review” by Leslie Allan