Donald Hoffman's Conscious Realism

Critical note on Donald Hoffman's form of idealism

Citation Information

Allan, Leslie 2020. Donald Hoffman's Conscious Realism (draft), URL = <>.

Photo of Professor Donald Hoffman

Professor Donald Hoffman

14 Jul 2020    Initial draft release

I'm planning on writing a critique of Donald Hoffman's form of idealism, which he calls 'conscious realism'. The following is my current scratch notes collecting my various arguments. To engage in a discussion about Hoffman's theory, visit this Facebook post >

and join the thread here >

1. Introduction

Donald Hoffman's metaphysics contains three components:

  1. Fitness Beats Truth (FBT) Theorem
  2. Interface Theory of Perception (ITP)
  3. Conscious Realism

The Fitness Beats Truth (FBT) Theorem is the result from a mathematical modelling of selective pressures during the evolution of species. That leads Hoffman to posit a pictorial representation of sensory perception; his Interface Theory of Perception (ITP). This theory pictures each species having a species-specific perceptual interface modelled on the metaphor of icons on a desktop. With his third component, he put the first two pieces together to posit that the real world consists only of conscious minds. As Hoffman explains, a key motivator for him in rejecting realism is the scant progress made in the mind-body problem. He describes this position as a form of idealism, so it's unclear why he labelled it as "Conscious Realism", taking his opponents "realist" label as his own.

I'll deal with each of his three components in turn, highlighting what I think are some of the key problems. He uses FBT/ITP to try and bolster his conscious realism, so I'll start there and then progress to his metaphysical thesis.

2. Fitness Beats Truth (FBT) Theorem/Interface Theory of Perception (ITP)

Hoffman summarizes his Fitness Beats Truth (FBT) theory thus:

... analysis of perceptual evolution using evolutionary game theory reveals that veridical perceptions are generically driven to extinction by equally complex non-veridical perceptions that are tuned to the relevant fitness functions. Veridical perceptions are not, in general, favored by natural selection. This result requires a comprehensive reframing of perceptual theory, including new accounts of illusions and hallucinations. This is the intent of the interface theory of perception, which proposes that our perceptions have been shaped by natural selection to hide objective reality and instead to give us species-specific symbols that guide adaptive behavior in our niche.

[p. 1, 'The Interface Theory of Perception', The Stevens' Handbook of Experimental Psychology and Cognitive Neuroscience]

Hoffman likens our perception of physical objects to our use of icons on our computer desktop:

Suppose that there is a blue rectangular icon in the upper right corner of the desktop for a text file that you are editing. Does this mean that the text file itself is blue, rectangular, or in the upper right corner of the laptop? Of course not. Anyone who thinks so misunderstands the purpose of the desktop interface. No features of the icon are identifiable with any features of the file in the computer. Moreover, one would be hard pressed to find a natural sense in which the icon is a veridical representation of the file. However, the icon is intended to guide useful behaviors. If, for instance, you drag the blue icon to the trash you can delete the text file; if you drag it to the icon for an external drive, you can copy the file.

[p. 1484, The Interface Theory of Perception]

Let me start by saying that I have a lot of sympathy with Hoffman's IPT, as do many, if not most, neuroscientists. What he says about how our perception of the physical world is mediated is not remarkable given what neuroscientists have known for several decades about the neural cognitive processes behind illusions and the top-down processing of sensory information. I think Metzinger puts it well when he writes:

... a fruitful way of looking at the human brain, therefore, is as a system which, even in ordinary waking states, constantly hallucinates at the world, as a system that constantly lets its internal autonomous simulational dynamics collide with the ongoing flow of sensory input, vigorously dreaming at the world and thereby generating the content of phenomenal experience

[Metzinger, T. 2003. Being No One: The Self-model Theory of Subjectivity, Cambridge, MA: MIT Press, p. 52].

Philosophers of perception and epistemologists call this the 'veil of appearance'. None of this is new or remarkable for a scientific realist. Hoffman goes much further by ditching realism altogether. He makes much of his claim that perceptions reveal nothing of the external world. As he writes in his paper, 'The Interface Theory of Perception' with Singh and Prakash: 'The interface theory of perception claims, on evolutionary grounds, that we should expect none of our perceptions to be veridical.' and 'Thus, according to the interface theory ... indeed all perceptions are fundamentally non-veridical'. [2015]

In his interview with Joel Frohlich, Hoffman says: 'all the stuff that we're seeing, it's a hallucination in the sense that it's just a visualization tool that doesn't resemble reality'. []

1.1 Overstatement

Hoffman may have overstated his case. His Fitness Beats Truth (FBT) theorem [Fitness Beats Truth in the Evolution of Perception] does not show all that he says it shows. It may show that in the long run that fitness beats truth most of the time, but evolution is an ongoing process. So, in the short run, with constant genetic variation resulting from spontaneous mutations and the random pairing of alleles during sexual reproduction, some members of a species will sense truth to at least some extent.

2.1 Overstatement

But even in those cases in which fitness is maximized through selection, there remains some mapping to external reality, even if it is not homomorphic. Otherwise, to use one of Hoffman's examples, the organism won't get the water it needs to survive [line 176,]. Michael Shermer makes the same point when he writes, 'Finally, why present this problem as an either-or choice between fitness and truth?' ['Did Humans Evolve to See Things as They Really Are?']

Other writers have picked up this same point, with Jonathan Cohen in his paper, Perceptual Representation, Veridicality, and the Interface Theory of Perception [] and Michael Vlerick summing up this more nuanced view in his 'Natural Selection Does Care about Truth' [p. 66f.,].

In fact, Hoffman seems to concede this point in an interview with Joel Frohlich that our perceptions are truth-tracking to some extent when he says: 'So the idea will be that evolution has shaped us with a very simplified interface that's been shaped mostly to report the stuff that's going to keep us alive.' The example that he gives of how our perception of distance is 'representing' fitness cost further concedes this point []. So, according to Hoffman, our perceptual systems are 'representing' objective facts about fitness cost and 'report' information to us about objective reality to the extent needed to keep us alive.

3.1 Evolution - mimicry

Another objection is that the evolutionary efficacy of mimicry indicates that organisms do sense reality at least to some extent. As Kevin Dickinson writes:

Hoffman would argue we see an icon that represents a snake, not a snake. But then why do nonpoisonous snakes evolve colorings to match poisonous ones? If there is no objective reality to mimic, why would mimicry prove a useful adaptation, and why would the interfaces of multiple species be fooled by such tricks?

['Did we evolve to see reality as it exists? No, says cognitive psychologist Donald Hoffman.']

Michael Shermer makes the same objection in his 'Did Humans Evolve to See Things as They Really Are?' at

4.1 Faulty methodology

Rainer Mausfeld advances a more general objection to Hoffman's approach. He finds serious problems with Hoffman's assumption that the notions of 'objective reality' and 'truth' have any role to play in biological theories of perception. ['Notions such as "truth" or "correspondence to the objective world" play no role in explanatory accounts of perception']

Hoffman responds to this objection by distinguishing between 'proximate' questions about internal mechanisms and 'ultimate' questions about the evolutionary development of those mechanisms. I find this answer a satisfactory rejoinder to Mausfeld.

Mausfeld also advances a number of conceptual objections to Hoffman's ITP theory and takes issue with Hoffman's use of selective constraints in the development of perceptual systems [p. 1539]. As an expert in the field, he observes that 'I know of no arguments from evolutionary biology that support HSP's claim that 'the distinction between fitness and truth is central to evolutionary theory.'' I think these objections remain outstanding.

5.1 Evolution counterexamples

In his paper, 'Usefulness Drives Representations to Truth: A Family of Counterexamples to Hoffman's Interface Theory of Perception', Manolo Martínez provides a number of empirical counterexamples to Hoffman's thesis that fitness always beats truth. He shows that Hoffman's simple model is accurate in only those cases in which an organism receives information from one source. Where an organism makes judgments based on two independent sources of information to ascertain utility, sending and receiving truthful signals promotes fitness.

6.1 Mischaracterize realism

Hoffman assumes without argument that a perception is veridical if and only if there is an isomorphic relationship between the quality of the perception and the true state of affairs. As he writes:

First, is the vocabulary of our perceptions isomorphic to aspects of objective reality so that our language of perceptions could, in principle, describe the objective truth? Second, if so, do our perceptual systems, using that vocabulary, in fact succeed in describing the true state of affairs in the world?

[p. 1482, 'The Interface Theory of Perception']

He is even more explicit in linking realism with positing an isomorphic relationship between features of the world and our perceptions when he writes that for a realist, 'the relation between interface and world is, on appropriately restricted domains, an isomorphism' [p. 14, 'The Interface Theory of Perception: Natural Selection Drives True Perception to Swift Extinction']

However, this grossly mischaracterizes realism, putting his own excessively stringent requirement on what a perception needs to satisfy for it to be veridical. For example, a non-isomorphic function between the world and our perception is the logarithmic dampening relationship between perceived loudness and actual sound intensity. Now, no one would suggest, other than Hoffman and his followers, that our perception of sounds is not veridical because of that. Jonathan Cohen also presents a strong case that the perceptions Hoffman labels as non-veridical are in fact veridical [Perceptual Representation, Veridicality, and the Interface Theory of Perception

Without realizing it, in his Reply to Objection 2 in his 'The Interface Theory of Perception' [2015], Hoffman presents the case for scientific realism of the 'structural realism' variety:

If our theory attributes some structure to the world W, and posits some functional relation P:WX between the world and our perceptions that is not veridical, we can still deduce from W and P what measurement results we should expect to find in X. The methodology of science is not so fragile that it fails entirely if P happens not to be some simple function, such as an isomorphism.

[p. 1500,]

Hoffman is right that the scientific enterprise survives the non-isomorphic relations between some states of world W and our perceptions of it. And with it, structural realism. Our non-simple, non-isomorphic perception of loudness is a paradigm case of the structural integrity of our objective perceptions of the world and one that Hoffman recognizes.

7.1 Theoretical inconsistency

Let's assume that Hoffman is right in thinking that 'all perceptions are fundamentally non-veridical'. Now, I'm not an expert in the theory of evolution. However, even without knowing a lot about natural selection and how it works in detail, Hoffman's hypothesis just seems self-refuting. Hoffman is the result of human evolution and yet can discern many facts grounded in observation and analysis.

Here is just one such fact about the world that Hoffman discovered from his observations of evolutionary processes and interacting with his peers. He states that the classic argument that veridical perception offers a competitive advantage 'misunderstands the fundamental fact about evolution, which is that it's about fitness functions — mathematical functions that describe how well a given strategy achieves the goals of survival and reproduction.' [2016 Interview with Donald Hoffman]

If there is no world external to the mind of biological organisms undergoing selective pressures in their environments, then how can Hoffman have found out that fact about just such a world?

Now think of how many physical computers Hoffman operated, how many academics he talked with in their offices, how many telephone calls he made. All of this while manipulating these 'computer' icons, 'academic' icons and 'telephone' icons as part of his research: manipulations of 'icons' that he says in the end are all 'non-veridical'.

Or take this other fact that Hoffman knows about the world:

The environment in which our species evolved is a highly structured place, containing many regularities. Light tends to come from overhead, there is a prevalence of symmetric structures, objects tend to be compact and composed of parts that are largely convex, and so on. Over the course of evolution, such regularities have been internalized by the visual system (Feldman, 2013; Geisler, 2008; Shepard, 1994).

[p. 1490, 'The Interface Theory of Perception']

If the operation of Hoffman's eyes and visual system are always non-veridical, how can he know so much about how they evolved and how they work? He seems to want his cake and eat it too.

If Hoffman's perception of a mind-independent external world with its biological organisms and selective pressures is all 'non-veridical', then so is any Hoffman theory built on it, no matter how elegant the mathematical models he produces. Hoffman faces the horns of a dilemma of his own making. Either the observational data he uses to produce his theory is veridical or it is not. If the former, his FBT theory is false as his observational data tracks truth. If the latter, his FBT theory is false as it is based on false premises.

Paul Austin Murphy makes exactly this point in his little piece, 'Donald Hoffman's Long Jump From Evolutionary Biology/Theory to Highly-Speculative Philosophy'. He writes:

Hoffman does and does not believe that there's a reality as it is. He believes that there is a reality as it is when he discusses evolutionary theory/biology (i.e., when discussing our ancestors). And he doesn't believe there is a reality as it is when it comes to his philosophical position of conscious realism.


Hoffman tries to get around this objection in his reply to Objection 3 in his paper, 'The Interface Theory of Perception'. He writes that his mathematical proof that natural selection does not favour veridical perceptions 'does not entail that all cognitive faculties are not reliable' and then proceeds to defend the hypothesis that perhaps our ability to do maths and logic is accurate [p. 1500,].

However, that's beside the point. Hoffman's mathematical game theory manipulates the conditions for the evolution of organisms in a natural physical environment. His mathematical games have content. If the content of those games (particular organisms with particular properties existing in particular environments) do not portray what he says they portray, then any amount of mathematical manipulation will lead to erroneous results. If we can add flawlessly two and two to deduce four, that is of no help in adding two apples to two apples to arrive at four apples if the apples are not really apples, but oranges. As the saying goes, 'garbage in, garbage out'.

In his same-titled 'The Interface Theory of Perception', he answers a similar objection that his FBT assumes the truth of the theory of biological evolution with all its attendant physical entities; the very thing he is trying to disprove [Reply 4. p. 10,]. Here again, Hoffman defaults to pointing to the 'algorithmic core' of evolutionary theory, devoid of its ontological commitments. As he writes, 'Our theories are ladders to new levels of understanding, and sometimes a new level of understanding leads us to kick away the very ladder that led to it.' [p. 10]

However, by kicking away the very entities that drive the mechanisms of evolution, he leaves evolution a process without a subject. If Hoffman ends by denying the subject matter of evolution, what is there for reproduction and natural selection to work on?

In his paper, Objects of Consciousness, Hoffman makes another attempt at deflecting the objection that his conclusion that all of perception is non-veridical is self-defeating. He writes in response:

We claim that perception evolved by natural selection. Call this statement E. Now E is indeed informed by the results of experiments, and thus by our perceptions. We observe, from evolutionary game theory, that one mathematical prediction of E is that natural selection generically drives true perceptions to extinction when they compete with perceptions tuned to fitness.

Suppose E is true. Then our perceptions evolved by natural selection. This logically entails that our perceptions are generically about fitness rather than truth. Is this a contradiction? Not at all. It is a scientific hypothesis that makes testable predictions.

[p. 17, Objects of Consciousness]

The problem with Hoffman's response here is that whether the conclusion, 'Natural selection generically drives true perceptions to extinction', makes predictions or not is wholly irrelevant to whether relying on perceptual evidence to support E contradicts the conclusion.

The following is a mutually inconsistent set.

D             Perception supports E

E              Perception evolved by natural selection

F              Natural selection generically drives true perceptions to extinction

Hoffman concedes D. Now, even if we grant that we know F is true without using our perceptual capacities, we still need to remove at least D or F from the syllogism to make it a consistent set.

Also, there is a certain irony in Hoffman relying on what he says are non-veridical perceptions to test the truth of a scientific hypothesis.

8.1 Theoretical inconsistency

The situation for Hoffman is even direr than this. Hoffman emphasises the point that not even our perception of space-time is veridical. He tells us 'It is this algorithmic core that is used by the FBT Theorem to conclude that our perceptions of space-time and physical objects do not reflect objective reality.' [Reply 4 p. 10,]

However, this algorithmic core, based as it is on Dawkin's 'universal Darwinism', is predicated on 'any group of entities that undergo transformations in terms of a change in probabilities between generations or iterations.' [Universal Darwinism as a Process of Bayesian Inference]

Now, notions of 'transformations', 'change', 'generations' and 'iterations' necessarily occur in time. Central to the concept of 'evolution' is change over time—even more so with the axioms of algorithmic Universal Darwinism used by Hoffman.

If the Universal Darwinism algorithms used by Hoffman, in combination with other assumptions, entail that one of the central axioms of Universal Darwinism is false, that's a signal to Hoffman that either his acceptance of Universal Darwinism is false or his conclusion that there is no time is false. He can't have it both ways. But it seems he wants to. In the formal axiomatic presentation of his conscious realism theory, he readily and unblinkingly relies on the concept of time throughout his entire treatise. For example, he writes: 'The idea is that at each step of the dynamics each of the four kernels acts simultaneously and independently of the others to transition the state ... to the next state.' [p. 10, Objects of Consciousness]

9.1 Theoretical inconsistency

For Hoffman, the situation is no better with his rejection of our perception of space. Even if we grant that only conscious entities exist, our category of space is real. For example, within our visual field, that content of our visual experience we call our 'left hand' is to the left of our 'right hand'. What we call the 'Sun' in our visual field rises above what we call the 'horizon'. Even for Hoffman, when he writes about the 'icons' on our 'desktop', he observes how 'a file icon is dragged to the trash' [p. 13, The Interface Theory of Perception: Natural Selection Drives True Perception to Swift Extinction]. These are all spatial relationships integral to the way our perceptual experiences manifest.

10.1 Theoretical inconsistency

Hoffman liberally uses biological explanations of adaption occurring in real time when doing so advances his thesis. In his paper, 'The Interface Theory of Perception: Natural Selection Drives True Perception to Swift Extinction', he writes:

A backward retina, for instance, with photoreceptors hidden behind neurons and blood vessels, is not the 'best' solution simpliciter to the problem of transducing light but, at a specific time in the phylogenetic path of H. sapiens, it might have been the best solution given the biological structures then available.

[p. 2, 'The Interface Theory of Perception: Natural Selection Drives True Perception to Swift Extinction']

In a telling comment, Hoffman informs us that his FBT/ITP 'entails that DNA does not exist when it is not perceived' [p. 11]. The problem here is that DNA has only been perceived within the last century. With no DNA existing for the previous fourteen billion years or so, there is no mechanism of variation and nothing for selection to work on. Without known existing entities to work on, that leaves us with no reason to hang on to the theory of evolution and leaves Hoffman with no reason to generate mathematical simulations—except perhaps to satisfy his own intellectual curiosity.

Hoffman tries to meet this objection by pointing out that:

Evolutionary changes in genes and body morphology can be modeled by evolution whether those genes and bodies are viewed as mind-dependent or mind-independent. The mathematics does not care. Nor does the fossil evidence. A dinosaur bone dated to the Jurassic can be interpreted along physicalist lines as a mind-independent object or, with equal ease, as a mind-dependent icon that we construct whenever we interact with a certain long-existing system of conscious agents.

[p. 111 Conscious Realism and the Mind-Body Problem]

Now, it may appear that Hoffman has up his sleeve an anti-realist interpretation of the evolution of organisms that is just as rich and fruitful as the scientific realist version. Not so. The mind-dependent 'dinosaur bone' he mentions here is simply a mathematical model of how our visual systems present a bone without Hoffman and his colleagues having done any of the work on how a fossilized bone millions of years old is embedded within the theoretical framework of a network of consciousness-only agents. (For more on this, see below.) It seems that crucial research program has not even begun.

Hoffman tells us:

For the conscious realist there is, no doubt, interesting and fundamental work to be done here: We want a rigorous mathematical theory of the evolution of conscious agents which has the property that, when this evolution is projected onto the relevant MUIs, it gives us back the current physicalist model of evolution. That is, we must exhibit physicalist evolutionary models as special cases, in fact projections, of a richer and more comprehensive evolutionary theory.

[p. 111 Conscious Realism and the Mind-Body Problem]

I'm not holding my breath waiting for this richer and more comprehensive anti-realist evolutionary account of dinosaur bones and the birth of the universe.

11.1 Parasitic on realism

Hoffman tries to use a reductio ad absurdum form of argument to counter 'metaphysical realism'. He argues that if the theory of evolution by natural selection is true, then nothing we perceive is veridical. The problem here is that that fact doesn't entail that 'metaphysical realism' is false. It only entails that we can't sense faithfully the properties of those things existing in the world external to minds. In fact, Hoffman's argument presumes such mind-independent objects to exist for his argument to work; that is, just those objects that provide the selective pressures for fitness to evolve.

12.1 Self-refuting

As an illustration of the above point, consider this. In Hoffman testing his FBT hypothesis, he says:

... we must include strategies that see none of the true facts, some of the true facts, and all of the true facts. Even if we suppose that human perception is veridical today, we must consider all possible strategies, veridical or not, in order to explore the plausible hypothesis that we evolved from species whose perceptions were not veridical.

[p. 1482, 'The Interface Theory of Perception']

In this scenario, it is Hoffman himself who is evaluating whether the test subjects see the 'true facts' or not. But Hoffman is a member of the species H. sapiens, a species he says for whom 'none of our perceptual experiences are literally true of the world' [p. 1489, 'The Interface Theory of Perception']. The blind leading the blind. His thesis is its own form of reductio ad absurdum.

13.1 False analogy

In contrasting realist strategies with 'strict interface' strategies in which perception does not preserve any structures of the world, Hoffman draws on his desktop icon analogy. Here, he is quite explicit in writing: 'No features of the icon are identifiable with any features of the file in the computer.' [p. 1484, The Interface Theory of Perception]

However, in dismissing non-representationalism he may be pressing his analogy too far. Clearly, the icon on our desktop is representing a file in some respects. For example, as with a file, it is self-contained within defined boundaries. Like a file, it is movable. To move the file to a different folder, I move the icon. Like a file, it is deletable and editable. It's a mistake to think that to represent the file with some level of veridicality, the icon needs to be identical to the file. Jonathan Cohen drives home this point in his paper, Perceptual Representation, Veridicality, and the Interface Theory of Perception [pp. 15f,]

As with desktop icons, we can also dig behind the level of appearance to uncover the underlying processes and structures. With desktop icons, we can investigate how moving an icon into another folder icon with our mouse changes the electrical patterns on the hard disc. Likewise, we investigate how the various colours of a solid body represent various electromagnetic wavelengths of light reflected by the body and how they interact with our eyes and visual cortex.

14.1 Faulty methodology

Using Monte Carlo simulations [p. 1486, The Interface Theory of Perception], Hoffman tries to show that natural selection favours a strict interface strategy over naïve realist and critical realist strategies. However, he is only able to demonstrate that using the contrived parameters he fed into his simulation. For the critical realist strategy, if he had set the perception of blue to coincide with a resource quantity between, say, 40 and 60, then that organism would be as finely tuned as the organism using the strict interface strategy. Hoffman choosing to break the colours for the critical realist strategy at precisely the mid-point of the Gaussian payoff curve was an entirely arbitrary choice that just happened to suite Hoffman's FTB hypothesis. And that handicap for the realist strategies results from his methodologically arbitrary choice in carving up the resource map with an even number of colours (i.e., 'where the perceptions of each player are limited to just four colors [p. 1486]. If he had chosen an odd number of colours to input into his mathematical simulation, such as 3, 5, or 7, a single colour would have ranged over the resource quantity with the highest payoff for both the realist strategies and the strict interface strategy. In Hoffman's game, the strict interface strategy was guaranteed a win because he had tied one hand behind the back of the realist strategists.

15.1 Self-refuting

Is it really the case that all of our perceptions are non-veridical? Take again Hoffman's case study using the perception of the quantity of a resource. [p. 1486, 'The Interface Theory of Perception'] One such resource is water. Now picture yourself sitting in front of a very large transparent tank that is being gravity-filled at a constant rate with water. We know that the tank is being filled at a constant rate because the force of gravity is constant and the water is being feed through a fixed diameter tube.

Now Hoffman would have us believe that although the volume of water in the tank appears to be increasing, it is not in fact so. For Hoffman, when the tank appears to be two thirds full, it could in reality be one third full or it could be two thirds full [green bands in Figure 3]. You just don't know. The quantity you think you are perceiving is a 'you know not what'. Even more absurd, for Hoffman, when you perceive the tank as empty, it could in reality be full [red bands in Figure 3].

Hoffman then applies this absurd conclusion to all of the other properties we sense. These include temperature, shape, velocity, hardness, etc. If we cannot in reality determine the scalar quantities of these properties, then how do Hoffman and other scientists practice science? If a hydrologist measures the volume of water as, say, 70 cubic litres, and we believe Hoffman, the volume could be anything. It could be one cubic litre or it could be 1,000 cubic litres. We just don't know. How then can we have a science of hydrology, or cosmology or biology?

Now, if Hoffman and other scientists can't say anything about the properties of biological organisms and the environments in which they live, then what are we to make of the entities that populate all versions of evolutionary theory? If cells, DNA, enzymes, fossils, mating pairs, predators, food, water, etc., are all 'you know not what'; if they are all non-veridical 'icons' representing 'you know not what' properties, then Hoffman needs to tell us how we can construct a theory of evolution in the first place. Hoffman appears hoist on his own petard. Alternatively, if he insists on using evolutionary biology to mount his case, he has already disproved that all perceptions are non-veridical. These are the horns of the dilemma that Hoffman stares into.

The upshot here is that his proof that all of our perceptions are non-veridical assumes the very realist interpretation of evolutionary biology that he seeks to disprove. His proofs rob from the same conceptual framework he endeavours to show to be fundamentally mistaken.

16.1 Evolution counterexamples

How did Hoffman get to this point of absurdity? One reason is that his mathematical model is based on a very simple organism that has only four possible percepts representing a wide scalar range of resource quantities. Hoffman mentions one such resource that organisms need to survive: 'Not enough water and one dies of thirst; too much and one drowns; somewhere in between is just right'. [p. 1486, 'The Interface Theory of Perception'] This is the kind of organism that would have first evolved some billions of years ago. Now compare that to Homo sapiens today.

Hoffman assumes without argument that the simple organism with only four percepts using the useful strict interface strategy will remain unchanged over the subsequent billions of years of evolution. Contrast that simple organism with a current Homo sapiens brain contains some 80 billion neurons with some 100 trillion connections between them. We are able to discern orders of magnitude more differences of quantities of water than just four. Hoffman's assumption that his highly simplistic model characterizes all of the strategy generation and selection forces guiding evolution throughout the last few billions of years seems entirely fanciful.

In his paper, 'The Interface Theory of Perception: Natural Selection Drives True Perception to Swift Extinction' [p. 20,], Hoffman recognizes the simplicity of a similar mathematical model and suggests how the models may be developed to more accurately reflect natural ecosystems. He states that these more complex models will allow scientists to determine at what level of complexity a truth strategy will prove more advantageous than a simple interface strategy. He bets there will be none of interest. But, for Hoffman, the jury is out.

A second reason Hoffman got to the point of absurdity is that his mathematical model premises a direct relation between perception and action. This was true for the earliest simplest organisms. However, it is clear that in our evolutionary history, the sensory function was complemented with both an environment modelling function and an executive function. So, today, when we are hungry and sense an apple, we can decide to eat it now or later. And our decision depends on the model of the external world we construct. If our belief is that eating the apple will raise the chagrin of the person who owns it, we may decided not to eat it all. Now, none of these complexities about our biological capacities and their evolutionary origins figures in Hoffman's mathematical model. He simply assumes, against the evidence, that if organisms were simple one-directional stimulus-response mechanisms billions of years ago, they must also be now. Michael Vlerick has more to say on the complexities of our cognitive capacities and their evolution in his 'Natural Selection Does Care about Truth' [].

17.1 Mischaracterize realism

At one point in his paper, 'The Interface Theory of Perception', Hoffman appears to conflate scientific realism and hybrid realism with naïve realism, being the view that our perceptions always reflect reality. He seems to think that because 'there are obvious cases where our perceptions radically disagree with our careful measurements' (as when it seems the sun, moon and stars all look equally far away, that this someone entails that the 'very notion of veridicality itself ... is void'. [p. 1497, 'The Interface Theory of Perception']

But why should the fact that our senses sometimes deceive us mean that they always deceive us? If I lay out marbles along a ruler laid out on the floor, how is it that my perception of the space between each marble is non-veridical; our misperception of the distance to the sun, moon and stars notwithstanding? In fact, neuroscientists have found in the mammalian brain neuronal grid cells whose firings map out evenly spaced locations in the environment. See, for example,
1. Christian Balkenius and Peter Gärdenfors 2016 'Spaces in the Brain: From Neurons to Meanings'
2. Moser E. I., Kropff E., Moser M. B. 2008. 'Place Cells, Grid Cells, and the Brain's Spatial Representation System' Neuroscience 31, 69–89. 10.1146/annurev.neuro.31.061307.090723
3. Amy McDermott, 'Neurons in the Hippocampus Can Make Several Different Maps of the Same Environment'

This neuronal mapping of distance adds independent confirmation to the thesis that our perception of distance at human sizes is largely veridical. It's what we would expect occurring in the brain if we reasonably accurately judged distance most of the time. How does Hoffman's FBT theory account for this consilience of evidences for veridicality?

18.1 Self-refuting

If, according to Hoffman, we can't judge distance veridically, then how are we to read Hoffman's explanation of his FBT thesis? In his 'The Interface Theory of Perception' [p. 1486,], he asks us to look at his explanatory diagrams. Look at the 'Resource Quantity' axis in his diagram labelled as Figure 2. If our perception of distance is non-veridical, then when we look at the '50' resource quantity point that appears half way between the '0' and '100' anchors, that point could in actuality be mapped to either around 30 or 70, just as the perception of green maps to either of those resource quantities for his test strict interface strategy organism (pictured in Figure 3, p. 1486). Ironically, if Hoffman's FBT thesis were true, that very non-veridicality he posits prevents readers of his paper understanding his own diagrams explaining his theory.

19.1 Self-refuting

Hoffman's Interface Theory of Perception (ITP) can be seen as the Comic Book View (CBV) of reality. Just as Hoffman's 'icons' are tuned for Homo sapiens' fitness, comic book characters are tuned for our pleasure. Just as with Hoffman's 'icons', they are a fiction and hide us from reality. Comic books are our escape from reality. For Hoffman, 'icons' are a  'fiction shaped by natural selection ' [p. 1503,], with the upshot that  'We see none of reality truly ' [p. 30,].

Paradoxically, however, Hoffman seems to think that by mining the 'icons' on our 'desktop', we can find out facts about this reality. Hoffman seems to think that by looking more closely into our 'icons', we can find out that our perceptions are tuned for fitness. And by looking more closely at the 'desktop', we can find out that space and time don't really exist. But if the 'icons' and the 'desktop' are a complete fiction designed to hide reality, then that's as fruitful as mining a Superman comic to discover the nature of Kyrptonite and its effects on Superman. Sure, we can find out a lot about Superman and his weaknesses by reading comic books more thoroughly. But that will tell us nothing about the real world.

If there are in reality no Homo sapiens, if there are in reality no natural environments and if there are in reality no resource shortages, then there is in reality no process of evolution. If there is no process of evolution, then there is no truth to be gained about the real world by simulating evolution mathematically. Similarly, if there are no electromagnetic fields, if there are no photons and electrons, if there is no double-slit experiment, if there is no quantum entanglement, then there is no quantum indeterminancy. Again, there is no truth to be gained about reality by drawing mathematical models of quantum effects.

20.1 Parasitic on realism

Hoffman's replies to Objection 3 [p. 8f., 'The Interface Theory of Perception' [] about how, if our model of reality is not relatively accurate, it is that we can land a spacecraft on Mars with pinpoint accuracy. Hoffman's reply to this objection makes it seem as if it's simply a matter of getting our hand-to-eye coordination right—just as a subject manages to get around quite well after a while with an inverted headset on. As Hoffman writes: 'we can have very predictable (and fitness enhancing) perception-action interactions via that interface, interactions such as landing a spacecraft on Mars.'

Hoffman then goes on to explain how his Invention of Symmetry Theorem (IOS) theorem can map, using symmetry, planarity and compactness, perceived shapes in a 3D space to another non-actualized dimension. The problem here is that the feat of landing a spacecraft on a planet millions of kilometres from Earth is not simply a matter of manipulating the 'icon' of a spacecraft with a joystick. That achievement is not like playing a space video game in which our only task is to co-ordinate our eyes and hands within a set of pre-established rules. Landing a spacecraft on Mars is the end result of centuries of hypothesizing and testing models of physics, astronomy and cosmology against reality so that we first understand what lies under the bonnet, so to speak. Space scientists only got to know how to build the spacecraft, send it into space and control its landing by first theorizing and understanding the underlying physics. Hoffmanian idealists are only then able to reverse engineer the mapping of manipulations of physical objects in space-time. Hoffman's post hoc mapping is only possible once scientists working within a realist paradigm have achieved their theoretical and technological advancements.

What scientists did was uncover the inner workings of nature so that they could predict how the spacecraft would perform in hitherto unknown environments—much like a video gamer working out how the microprocessors, power supply, etc., interact with software code to display the visual image she sees in her headset. No amount of looking more closely at the icons on her screen will allow her to predict what will happen if she performs a motion that is not within her known game rules. For that, she must understand how the virtual reality apparatus really works.

Consider the alternative Hoffmanian idealist approach to discovering what it takes to land a spacecraft on Mars. Space scientists will need to know, for one thing, how a spacecraft will behave travelling in space. They will need a theory of dynamics. For simplicity, reflect on Newton's achievements viewed from Hoffman's standpoint; the standpoint from which Newton is seen as a higher-level 'conscious agent' built up from many atomistic 'conscious agents' organized into a vast network of such agents. [Objects of Consciousness]

This 'conscious agent' known as Newton postulated his realistically interpreted Three Laws of Motion and his Universal Law of Gravitation. He had no option of building a Hoffmanian set of dynamical laws as at that time in the seventeenth Century he, just as we do today, had no access to a rich Hoffmanian idealist framework from which to build such a theory. (In addition, it's not possible to interpret Newton's theory qua physical theory non-realistically. See my Sec 3, The Existence of Mind-Independent Physical Objects

Newton's theory, in conjunction with the realist interpretation of auxiliary hypotheses (such as a theory of observation, a statement of initial conditions, and so on), allowed for the prediction of certain novel perceptual experiences; experiences that would not have been expected had it not been for Newton's postulates. These novel perceptual experiences included those experiences that we would describe as perceiving the existence and position of the hitherto unknown planet, Neptune, and perceiving the return of Halley's Comet in 1759. Furthermore, his theoretical system provided a novel derivation of a description of those experiences we call perceiving the progress of the moon's apogee.

My point here is that the Hoffmanian idealist can theoretically describe these novel perceptual experiences within their paradigm of an infinite network of 'conscious agents', just as they can describe the events and states of affairs preceding the successful predictions and postdictions. However, since it was from Newton's realist dynamics that these predictions were made, and not from some non-existent Hoffmanian version, Newton's predictive and postdictive success constituted independent evidence for Newtonian mechanics."

The same can be said for the confirmations of Einstein's Special and General Theories of Relativity, the Rutherford-Bohr atomic theory, the kinetic theory of gases and a host of other physical theories that space scientists relied on to get their spacecraft to Mars. The salient point here is that each of these theories, realistically interpreted, made bold novel predictions that were subsequently stunningly confirmed by independent observers. Conversely, Hoffmanian idealism had no part to play in the empirical confirmation of our best scientific theories. It is only able to 'explain' in the broadest and most ethereal of ways the realist's anticipation of novel phenomena post hoc.

21.1 Absurdity

Hoffman argues that evolution shaped our perception not to mirror truth, but to enhance our fitness. As he puts it: 'Perception is not about seeing truth, it's about having kids.' [p. 5, 'The Interface Theory of Perception']

If our perceptions are shaped by fitness payoffs—with having more children—then that raises a question: How does our ability to manipulate 'icons' in order to land a spacecraft on a body millions of kilometres from anyone aid reproductive fitness? Through advances in technology, we also now have the capacity to see molecules and atoms and to see distant galaxies. How does seeing those 'icons' help us have more children? In fact, a survey of population statistics reveals that scientists engaged in space travel and with researching atoms and galaxies have fewer children on average than those not educated in the sciences.

3. Conscious Realism

Conscious realism is Hoffman's proposed solution to the intractable mind-body problem in the philosophy of mind. How is it that inanimate matter gives rise to mental phenomena? Hoffman's answer to what the universe is made of is that the objective observer-independent world consists entirely of conscious agents operating within an infinite network of connections. [p. 103, Conscious Realism and the Mind-Body Problem]

22.1 Overstatement

In this universe, physical objects pop into and out of existence. Hoffman puts it this way:

In like manner, we create an apple when we look, and destroy it when we look away. Something exists when we don't look, but it isn't an apple, and is probably nothing like an apple


The first challenge for Hoffman is that under this scheme, 'metaphysical realism' may still be true. As Hoffman admits, there is something that continues to exist even when we are not looking.

23.1 Absurdity

There are deeper problems with Hoffman's view. If the apple ceases to exist when I'm not looking at it, then how can something that ceases to exist once I swallow it nourish me and keep me alive? For that matter, what stops me from falling from the sky when I'm not looking at the aeroplane wings on my flight to London? If it's someone other than me looking at the wings that keeps them existing, then what happens when all of the passengers look to the front of the plane, or fall asleep? What keeps the train moving on my journey when I'm no longer looking at the wheels? These are the same kinds of absurdities that George Berkeley faced with his version of ontological idealism. Berkeley's solution was to rely on the mind of God that continued to perceive apples, aeroplane wings and train wheels when none of us were observing them. Hoffman has closed off that option in his account.

24.1 Self-refuting

Another incisive objection that Kevin Dickinson points out is that if the icons on our desktop reveal nothing about reality, then perhaps my consciousness is just another icon. As he puts it:

If our perceptions of reality are merely species-specific interfaces overlaid upon reality, how do we know consciousness is not simply another such icon? Maybe the "I" of everyday experience is a useful fantasy adapted to benefit the survival and reproduction of the gene and not part of the operating system of reality.

['Did we evolve to see reality as it exists? No, says cognitive psychologist Donald Hoffman.']

This is a particularly devastating objection to Hoffman's thesis as at its core is the postulation of 'conscious agents' as distinct entities.

25.1 Collapse into solipsism

And what about other minds? We don't perceive them at all. They are not even represented as 'icons' in our perceptual field. We only perceive the physical bodies that they inhabit. If, on Hoffman's view, we should ditch our belief in physical bodies, then how more so should our clean up extend to other minds? It's hard to see how Hoffman's thesis does not lead us inexorably down the path to a thorough-going solipsism.

26.1 Heuristic sterility

In his interview with Joel Frohlich, Hoffman makes an attempt to coalesce his conscious realism with a theory of evolution (which he needs to support his move from FBT/IPT to his version of idealism). He speculates that

there is a sense of "fitness", in vast social networks. The more connections you have, in some sense, the more fit you are. And the less connections you have, the less fit you are. So Google has tons of connections and the owners of Google are billionaires, Hoffman has a very few and he's not a billionaire.

['Book Review and Author Interview: The Case Against Reality by Donald Hoffman']

OK. But how does that sense of evolutionary 'fitness' in disembodied social networks explain the evolution of the eye 'icon' that appears to perceive external physical objects via light waves reflecting off the surfaces off mind-independent physical objects? How does that 'fitness' schema explain the evolution of the 'icon' for cosmic microwave background (CMB) radiation that exists from some 13 billion years before conscious minds even arrived? How does that 'fitness' schema explain the evolution of our idea that objects have permanence even when no one is perceiving them?

Hoffman already relies on an explanation of the characteristics of the human eye as resulting from selective environmental pressures acting over a long period of time. In his 'The Interface Theory of Perception: Natural Selection Drives True Perception to Swift Extinction', he writes:

A backward retina, for instance, with photoreceptors hidden behind neurons and blood vessels, is not the "best" solution simpliciter to the problem of transducing light but, at a specific time in the phylogenetic path of H. sapiens, it might have been the best solution given the biological structures then available.

[p. 2, 'The Interface Theory of Perception: Natural Selection Drives True Perception to Swift Extinction']

How will Hoffman's alternative explanation in terms of 'fitness' in disembodied social networks look when there is no time and space for evolution to work in and no photoreceptors, neurons and retina to work on?

Here, Hofmann gives us a hope and prayer:

Let's look at those dynamics and see which one makes sense. And then that will give us some insight into what's going on in the realm of conscious agents, what they're up to, and then when we project that back into our spacetime interface, we should get evolution by natural selection or hopefully a generalization that makes new predictions beyond evolution by natural selection.

['Book Review and Author Interview: The Case Against Reality by Donald Hoffman']

What Hoffman gives us here is a promissory note for a research program that seems to not have even begun.

27.1 Absurdity

Realism about external physical objects explains naturally the singular identity of things that more than one person perceives. Hoffman's theory, on the other hand, generates puzzles that strain language conventions unnecessarily. Hoffman writes:

According to [multimode user interfaces] MUI theory, the objects of everyday experience – tables, chairs, mountains, moon – are not public. If, for instance, I hand you a glass of water, it is natural, but false, to assume that the glass I once held is the same glass you now hold. Instead, according to MUI theory, the glass I held was, when I observed it, an icon of my MUI, and the glass you now hold is, when you observe it, an icon of your MUI, and they are numerically distinct. There are two glasses of water, not one. And if a third person watches the transaction, there are three glasses.

[p. 97, Conscious Realism and the Mind-Body Problem]

Hoffman answers the patent absurdity of multiplying singular items by pointing to a virtual tennis game played by Bob and Tom. In this virtual game, Hoffman claims, both players can agree when Tom hits "the tennis ball" out of court [p. 97].

Yes, Bob and Tom can agree that they are playing with the same tennis ball. They do that in accordance with the linguistic rules we commit to when playing networked virtual games. However, they can't do that under Hoffman's proposed linguistic contortions. Under Hoffman's rendition, if Bob and Tom are playing with numerically different tennis balls (and in numerically different tennis courts), they can't be playing against each other in the same game of tennis. They must be playing two separate games of tennis. Contra Hoffman's claim, this numerical separation will actually mess up 'meaningful communication' between people trying to co-ordinate their actions. Under Hoffman's scheme, when Bob hits the ball into Tom's part of the court and Tom misses, Bob can't claim a point. Tom will complain that the ball that he missed is not the same ball that Bob had hit. They are different balls.

Likewise, if I steal your car, I haven't really stolen your car, have I? The car sitting in my driveway that looks identical to your car is not really yours. So, don't call the cops.

28.1 Absurdity

Hoffman continues:

According to MUI theory, everyday objects such as tables, chairs and the moon exist only as experiences of conscious observers. The chair I experience only exists when I look, and the chair you experience only exists when you look.

[p. 98, Conscious Realism and the Mind-Body Problem]

The implication here is that when I sit on a chair, I'm sitting on a conscious experience. And when I look at the moon through my telescope, I'm really looking at a conscious experience.

As Hoffman explains: 'We only see the chair icons we each construct each time we look.' [p. 98]

The absurdities only continue to mount. If a 'chair' is really a conscious experience, then, for Hoffman, when we see a chair, we are really seeing a conscious experience. There are really then two experiences going on: the 'chair' experience and the experience of seeing the 'chair' experience.

Keeping to Hoffman's virtual reality game analogy, is it not better for Hoffman to say not that the tennis ball is a conscious experience, but that the percept of the tennis ball is a conscious experience. Think of the language rules we use when we are playing a virtual reality game. When we play virtual tennis, we don't say that we are hitting a conscious experience around the court and we don't say that we are seeing a conscious experience when we see the virtual ball. Adopting my suggestion here allows Hoffman to say in real life, as in the virtual reality game, that we 'see the tennis ball' and that seeing the tennis ball consists in the having of the experience of a tennis ball.

Hoffman could avoid the other absurdity that we play with magic disappearing tennis balls in real life and in virtual reality tennis games by appealing to the notion that tennis balls are theoretical fictional entities by which we take an imaginative leap beyond our immediate experience. This approach leverages off the realist conceptual framework of mind-independent objects, but preserves the fictional character of his virtual reality analogy. Borrowing from the realist conceptual scheme is a disbenefit for Hoffman. However, perhaps this move is less debilitating than advocating absurd linguistic expressions.

29.1 Parasitic on realism

With his heavy reliance on the virtual games analogy, it's difficult to see how Hoffman can escape presupposing a realist conceptual scheme. Consider this. In defending the notion that Bob and Tom are playing with numerically distinct tennis balls while still speaking of "the tennis ball", Hoffman writes:

And there is no other tennis ball around to serve the role of public tennis ball. Thus public physical objects are not required for meaningful communication.

[p. 97, Conscious Realism and the Mind-Body Problem]

The thing to keep in mind here is that in this case, Bob and Tom both know that there are mind-independent physical structures and processes that generate the simulation of the 'public tennis ball'. Hoffman himself refers to how the 'supercomputer in the back room feeds signals to the helmet displays of Bob and Tom and each, in consequence, constructs his own tennis-ball experience' [p. 97]. Hoffman could object here that Bob and Tom might not 'know' that there is such a supercomputer working in the background. Perhaps there is some other set of structures and processes in place that generate the tennis ball experience. However, it remains the case that it is Bob and Tom's belief that there is such a supercomputer that warrants their confidence that they are playing the same tennis game and not locked into their own solipsist world. Even when we acknowledge the point that Bob and Tom could be wrong in their belief, the crucial point here is that Bob and Tom must have some belief in a set of structures and processes that are independent of them, yet common to both of their worlds, that generate the image of the tennis ball. It is this shared belief in a common source of their tennis ball images that warrants their language convention that is precisely denied Hoffman.

Now, Bob and Tom may be completely ignorant of supercomputers and how they process information and generate images in their headsets. But Bob and Tom accept that whatever the system is that generates the simulated tennis game, it is simulating the physical process that generates visual information and transmits it into their eyes. For Bob and Tom to accept that they are playing the same virtual game with the same tennis ball, they are assuming this second-order physical processing and generation of visual information that mimics the usual first-order perception of objects via mind-independent physical objects reflecting light-waves of particular wavelengths and intensities into their eyes.

In the absence of a worked out theory of a consciousness-only network that generates all of our perceptual experiences that rivals the explanatory and predictive power of our current realist theories of perception, Bob and Tom remain wedded to their realist assumptions underpinning their belief that they are playing the same tennis games with the same ball. The upshot here is that Hoffman's use of the virtual reality tennis game analogy throws him in to linguistic muddles and absurdities and serves to underscore how Bob and Tom can only play the game by making realist assumptions about the underlying metaphysics.

30.1 Collapse to solipsism

Hoffman infers the existence of conscious agents who exist independently of him by analogy with having first-hand experience of his own consciousness. Here is how he puts the argument.

According to conscious realism, when I see a table, I interact with a system, or systems, of conscious agents, and represent that interaction in my conscious experience as a table icon. Admittedly, the table gives me little insight into those conscious agents and their dynamics.

When, however, I see you, I again interact with a conscious agent, or a system of conscious agents. And here my icons give deeper insight into the objective world: they convey that I am, in fact, interacting with a conscious agent, namely you.

[p. 103, Conscious Realism and the Mind-Body Problem]

The question I pose to Hoffman here is: How does perceiving a physical body give that deeper insight, more so than tables? The 'you' icon, as it appears to Hoffman, is simply another 'physical body' icon. How do you know it's even conscious?

Further on, Hoffman tries to answer this quandary about other minds by suggesting we look in the mirror. When we look in the mirror, all we see is a physical face, all the while knowing that there is a consciousness behind the face 'icon'. Similarly, Hoffman suggests:

Other people see a face, not the conscious agent that is your deeper reality. They can, of course, infer properties of you as a conscious agent from your facial expressions and your words; a smile and a laugh suggest certain conscious states, a frown and a cry others.

[pp. 109–10, Conscious Realism and the Mind-Body Problem]

Here, in this crucial step in the argument, Hoffman leaps immediately from recognizing his own consciousness to other 'people' inferring your consciousness. But whether these other 'people' are conscious to begin with and can make such inferences is exactly the question at issue. If our 'user interface' hides reality, as Hoffman claims, then he hasn't really answered the question of his interlocutor: 'How do we get outside of our epistemic jail, the super-user interface?' [p. 110]

That other conscious agents exist in a vast network is a central axiom of Hoffman's MUI theory and his conscious realism. With due credit to Hoffman, he does concede that the inference to other minds is 'unavoidably fallible'. However, he does need to do much more work if he is to avoid a solipsist conclusion to his view that user interface 'icons' hide reality.

31.1 Parasitic on realism

In his section titled 'The Mind-Body Problem', Hoffman begins by promising us a scientifically and mathematically rigorous account of how conscious agents interact directly without intervening mind-independent physical objects and processes. He writes:

Conscious realism, by contrast, offers a scientific theory of the noumenal, viz., a mathematical formulation of conscious agents and their dynamical interactions.

[p. 104, Conscious Realism and the Mind-Body Problem]

He continues:

The ontology of conscious realism proposed here rests crucially on the notion of conscious agents. This notion can be made mathematically precise and yields experimental predictions (Bennett et al. 1989, 1991; Bennett et al. 1993a,b; Bennett et al. 1996).

[p. 105, Conscious Realism and the Mind-Body Problem]

And more:

We now have mathematically precise theories about how one type of conscious agent, namely human observers, might construct the visual shapes, colors, textures, and motions of objects (see, e.g., Hoffman 1998; Knill and Richards 1996, Palmer 1999).

[p. 106, Conscious Realism and the Mind-Body Problem]

Hoffman explains how these mathematical formulae show how one conscious agent constructs in their visual field colour, texture, motion, depth, etc. However, none of this is original to Hoffman's conscious realism theory. Hoffman informs us that his mathematical models are simply reinterpretations of realist approaches to perception. He readily concedes this point when he writes:

Almost without exception the authors of these perceptual theories are physicalists who accept HFD and conceive of their theories as specifying methods by which human observers can reconstruct or approximate the true properties of physical objects that, they assume, exist objectively, i.e., independently of the observer (a claim about physical objects that is explicitly denied by conscious realism). But each of these perceptual theories can equally well be reinterpreted simply as specifying a method of object construction, not reconstruction.

[p. 106, Conscious Realism and the Mind-Body Problem]

Hoffman accepts that at the core of these physicalist theories is the axiom that there really are true properties of mind-independent physical objects. Therein lay their predictive success; by proposing an invariant and known external cause of our perception. By contrast, the supposed predictive successes of Hoffman's mathematical models turn out to be not unique to Hoffman's conscious realism theory, but are parasitic on the successes of the realist research programs on human vision.

How easy is it for Hoffman to conscript the predictive successes of a realist view of perception as his own? Very easy. He tells us how:

I can pull the W out of the model and stick a conscious agent in its place and get a circuit of conscious agents. In fact, you can have whole networks of arbitrary complexity. And that's the world.

['The Evolutionary Argument Against Reality']

And he does just that in his paper, Objects of Consciousness, where he simply redefines the space-time world of physics W to one in which the 'world W consists entirely of conscious agents'. [p. 7 Objects of Consciousness]

Now, one mark of a progressive scientific theory is that it explains the predictive successes of its rival. For example, Einstein's Special Theory of Relativity explains the successful predictions of its rival and predecessor, Newtonian dynamics. These include the return of Halley's Comet and the existence and location of the planet Neptune. Einsteinian Relativity would not have got a Guernsey if it had merely restated Newtonian mechanics in non-Euclidian mathematics.

Hoffman gets our expectations right when he writes that:

We want a theory of consciousness qua consciousness, i.e., of consciousness on its own terms, not as something derivative or emergent from a prior physical world.

[p. 5, Objects of Consciousness]

That is the task he is yet to begin.

32.1 Heuristic sterility

A second problem is this. Hoffman announces that his reconstructions give 'mathematically precise theories about how certain conscious agents construct their physical worlds'. [p. 106, Conscious Realism and the Mind-Body Problem] The problem here is that his reconstruction shows only how one conscious agent constructs their world. His reformulation says nothing substantive about 'conscious agents and their dynamical interactions', which is his promise to us. It says nothing about how, when I get a headache from a rock falling on my head when no one else is around, this is the result of the actions of another conscious agent. It says nothing about how, when I look up and see the moon, my moon experience is the result of the action of another conscious agent.

Hoffman alludes to the task he has set himself and that I am talking about here in his example of how neuroscientists stimulating a brain cause the experience of phosphenes.

When, for instance, we stimulate primary visual cortex and see phosphenes, the cortex does not cause the phosphenes. Instead, certain interactions between conscious agents cause the phosphenes, and these interactions we represent, in greatly simplified icons, as electrodes stimulating brains.

[p. 108, Conscious Realism and the Mind-Body Problem]

It is exactly this specification of the dynamic interactions between the conscious agents that we are expecting from Hoffman and that we are missing.

33.1 Heuristic sterility

Another complication for which Hoffman's theory needs to provide some credible account is the synchronicity between our different sense modalities. How is it that every time I eat a tomato I experience its redness, its squishy sound, moist texture and sweet taste all at the same time? How does Hoffman's theory account for this regularity? When answering a question about how this multi-modality comes about, all Hoffman has to offer is that conscious experiences are fundamental. [p. 109, Conscious Realism and the Mind-Body Problem]

A realist account of multi-modal sense perception, on the other hand, provides a rich and fruitful story of how and why this synchronicity arises from a single cause; the single mind-independent physical tomato that possesses multiple sensory properties. Hoffman's theory, on the other hand, seems to draw a blank.

34.1 Theoretical inconsistency

In his paper, Objects of Consciousness, Hoffman considers the objection to his proposed six-part modelling of conscious agents that most of our mental processes are unconscious processes, hidden from phenomenal awareness. Hoffman accepts this, finding this opaqueness of most our own mental processing just another consequence of natural selection and his ITP. Nevertheless, he cautions that even though 'most of my mental processes are not directly conscious to me, but that does not entail that they are unconscious.' [p. 5, Objects of Consciousness]

But what reason does Hoffman have to think that these mental processes for which we are unaware are conscious at all? If evolution hides the true nature of these unperceived mental processes from us, perhaps they are not conscious processes at all. How would Hoffman know? Furthermore, being unperceived, they have no 'icon' to represent them to us. If 'icons' hide the underlying reality behind them, then how much more so events that sport no 'icon'?

Hoffman could respond here that these mental events for which we are unaware are theoretical constructs that will serve a function in his overall conscious realism thesis. That may be. However, if he allows veridicality to posited theoretical events that we do not experience directly, then why limit his model to posited atomistic conscious entities? His whole raison d'être behind his rejection of our belief in mind-independent physical objects was that this belief is unwarranted given that evolution drives non-veridical perceptions.  If he is now to allow theoretical entities that bypass his test of veridicality, then why stop at unperceived mental processes? For all Hoffman knows, these 'mental' processes for which we are unaware may have a mind-independent physical basis. These processes may not, at root, be mental at all. In fact, the realist neuroscience research program investigating unconscious processes has made substantial progress in our understanding of, for example, cognitive biases, obsessive compulsive disorders, drug addiction, and so on. It seems to me that Hoffman has abandoned his in-principle reason for continuing to deny a place for these physical explanations into his theoretical model.

35.1 Theoretical inconsistency

Hoffman formalises his conscious realism theory by first defining a 'conscious agent' as consisting of three processes: perception, decision and action. It may seem that what Hoffman means by a 'conscious agent' here is a complete higher-order entity with consciousness, such as a dolphin or a human being. He speaks of how a 'conscious agent' 'chooses what actions to take based on the conscious experiences it has' and how it 'interacts with the world in light of the decision it has taken'. [p. 6, Objects of Consciousness] Furthermore, in answering readers' qualms, he ascribes 'free will' to all conscious agents and goal-directed behaviour to some [pp. 14–15].

In spite of the teleological/intensionalist language Hoffman uses to describe a 'conscious agent', what he means by this is the atomic component of the world we live in. For example, he applies his model to visual perception where each conscious agent represents one computational function of a visual system, working iteratively to build a visual percept [pp. 9-10]. For Hoffman, then, each organism's visual system is comprised of multiple conscious agents working synchronously together to form the organism's visual image.

In this respect, Hoffman's theory draws on the atomistic elements of pantheistic micropsychism in which higher levels of conscious entities are built up by aggregates of atomic components. How does Hoffman borrow from panpsychism? The debt is illustrated in this piece where Hoffman writes:

'When others see your face, they open a genuine, but limited, portal into your conscious world. Which is not to say that your face is conscious. It's not. You are conscious. Your face is an icon in the interface of the viewer.

When I see a dog, my portal into consciousness is dimmer. I guess there is enjoyment of a bone and excitement by a squirrel. When I see an ant, my portal is dimmer still; I have little insight into the experiences behind my icon of an ant. With a rock, my portal is opaque; it offers no obvious insight into experiences behind the icon. My interface has, of necessity, finite limits; when it delivers a rock, it cries uncle — similarly, when it delivers atoms and molecules.'
[Imitation and Extinction: The Case Against Reality]

The difference between the two approaches is that pantheistic micropsychism allows for the reality of physical objects. Hoffman's conscious realism may be cast as pantheistic micropsychism without matter.

Hoffman recognizes that he has a big problem, along with advocates of pantheistic micropsychism, in combining the discrete elements of experience into a homogenous whole. As he writes:

For instance, one's taste experiences of salt, garlic, onion, basil and tomato are somehow combined into the novel taste experience of a delicious pasta sauce. What is the relationship between one's experiences of the ingredients and one's experience of the sauce?

[p. 11, Objects of Consciousness]

A more serious problem he recognizes is how to combine the individual subjects of experiences, the discrete conscious agents at the micro-level, to a unified conscious being at the macro-level, such as a human or dolphin. Here, Hoffman develops two mathematical theorems from which he draws the conjecture that 'any subset of conscious agents from the pseudograph, adjacent to each other or not, can be combined to create a new conscious agent' [p. 12, Objects of Consciousness]

Hoffman suggests triumphantly that this method of mathematical combination shows how 'introspection emerges, in an intelligible fashion, from the combination of conscious agents.' [p. 13] However, it's not at all clear how this introspection can occur as Hoffman, himself, repeats Coleman's conclusion that 'in so far as they [subjects] are points of view they are experientially distinct and isolated—they have different streams of consciousness' [p. 12]. In a later answer to an objector, Hoffman reinforces this inability of one conscious agent to experience directly the experience of another conscious agent. He writes: 'The qualia X of a conscious agent C are private, in the sense that no other conscious agent Ci can directly experience X.' [p. 14]

36.1 Heuristic sterility

A larger problem looms. How is Hoffman to delineate combinations of perceptual experiences into what we see currently as meaningful bundles? When I'm looking at a red tomato and smelling burning toast, how is it that the redness of the tomato is not bundled with the smell of burning? How is it that the roundness of a tennis ball combines with the tennis ball and not with the net? With a realist interpretation of our perceptual experiences, these combinations are explained easily and naturally as perceptual experiences are bundled with the individual physical object that causes in us those experiences. With Hoffman's vast, interconnected network of micro-conscious agents, it's difficult to see a principled way in which he can carve out perceptual bundles.

The same is the case with carving out minds. We delineate each mind we come across by identifying it with a physical body. Under Hoffman's scheme, how can he draw the boundaries between his mind and my mind in a way that is not arbitrary? How do the micro-conscious agents that make up my mind not belong to the mind of my best friend or my dog? The challenge here for Hoffman is how to carve up combinations of perceptual experiences and micro-conscious agents in a way that is not parasitic on the way we individuate mind-independent physical objects and minds.

Imbuing micro-conscious agents with perception, decision and action gives the initial appearance that these conscious agents identify with us and other primates. This tripartite nature also mirrors the operation of neurons, with their inputs, internal processing and outputs. However, unlike physical organisms and neurons, Hoffman's network of disembodied conscious agents do not afford him the heuristic richness of a substrate and an individuating principle that carves up entities into natural wholes.

37.1 Heuristic sterility

In next discussing the mental construction of physical objects, Hoffman moves from the incredible to the incomprehensible. He proposes that 'space-time and objects are among the symbols that conscious agents employ to represent the properties and interactions of conscious agents'. [p. 13, Objects of Consciousness]

In working through sets of complex equations [pp. 13f], Hoffman professes to 'observe that the harmonic functions of the space-time chain that is associated with the dynamics of a system of conscious agents are identical to the wave function of a free particle; particles are vibrations not of strings but of interacting conscious agents'. [p. 13]

Hoffman does this by identifying certain features of quantum theory with features of his conscious agents; features that he explicitly imported into his theory. The maths is beyond my capability, so I'll leave it to others to evaluate their relevancy and veracity. Let me remark, however, that with all the included complexities about eigenfunctions, Planck scale, Markovian dynamics, and so on, Hoffman affords us no insight into the most fundamental questions raised by his proposing that we do away with mind-independent objects.

Hoffman gives us no inkling of how a stone unseen by anyone falling off a cliff on to my head can give me a headache. Or why we mentally construct stars and planets that existed billions of years before any consciousness arose? Or why we conjure up forces of nature and particles so small that no one can perceive? All up, Hoffman gives us a very impoverished model of consciousness and of physical objects. We learn more about how human minds work from Plato and Aristotle writing more than two millennia ago.

38.1 Heuristic sterility

In his interview with Amanda Gefter, Hoffman says:

Here's the striking thing about that. I can pull the W out of the model and stick a conscious agent in its place and get a circuit of conscious agents. In fact, you can have whole networks of arbitrary complexity. And that's the world.

['The Evolutionary Argument Against Reality']

The obvious question raised here is: What independent evidence does Hoffman offer for this network of conscious agents? And what is his theory about the causal interconnections between these minds that give our sense-experience its regularity? What factors determine which atomistic conscious agents will combine to form more complex entities?  Why are the true connections and communications between conscious agents so opaque to the extent that what is presented to us is a gross mischaracterisation of reality at the most basic level? Why does this network of conscious agents appear positively deceitful?

Our modern theories of cosmology, physics, biology and neuroscience combined tell a comprehensive and complex story that answers our questions about the physical universe and our place in it. In addition, over the span of more than two millennia, we have accumulated countless instances of confirmed novel predictions that attest to the veracity of our models of reality. Of course, the 'hard problem' of consciousness remains in philosophy of mind and physicists are still grappling with dark matter and dark energy. In spite of these unanswered questions, we have made enormous strides in our understanding. Hoffman's theory, on the other hand, draws a big blank. In fact, it's just a promissory note for a theory that may or may not come later.

4. Conclusion

Hoffman is driven to his conscious realism schemata because, as he says, he was frustrated with the lack of progress on the mind-body problem. As I have tried to show in this critical note, ditching realism for Hoffman's version of idealism only serves to give away a theoretical framework that has, over the last couple of centuries, proved enormously fruitful, not just in the theoretical domain, but also in the way it has led to improved psychological and psychiatric treatments and helping with people with impaired sensory systems.

Giving all of this up for Hoffman's alternative schemata leaves us with:

  • basic problems with his FBT
  • linguistic confusions and absurdities
  • a discipline of evolutionary biology without a subject
  • a theory of networked conscious agents that so far has no explanatory value

Types of objections:

  • Overstatement
  • Heuristic sterility
  • Parasitic on realism
  • Theoretical inconsistency
  • Evolution - mimicry
  • Evolution counterexamples
  • Faulty methodology
  • Mischaracterize realism
  • Absurdity
  • Parasitic on realism
  • Self-refuting
  • False analogy
  • Collapse into solipsism

The mind-body problem has proved enormously intractable. However, the lack of a solution is not at all impeding advances in biology, neuroscience, physics, cosmology, etc. That we so far have not found a solution is, I suspect, at least partly the result of the fact that the human brain is complex beyond all imagining, with an adult brain hosting some 80 billion neurons with some 100 trillion connections between them. Couple that with the lack of conceptual tools that we have at hand. Philosophers of mind are proving essential here in formulating the problem and suggesting conceptual pathways.

I'm not expecting an answer any time soon. My view is that where we are at the moment is akin to where we were prior to Newton. Before Newton, we had two sets of physics. One set for the terrestrial realm, guided by Aristotelian dynamics. And other set for the extra-terrestrial realm guided by Ptolemy. It took Newton to forge a common language and conceptual framework to combine what seemed to be two entirely separate domains of enquiry.

Hoffman is right when he observes the immense challenges faced by his theory when he writes:

How can such an approach explain matter, the fundamental forces, the Big Bang, the genesis and structure of space-time, the laws of physics, evolution by natural election, and the many neural correlates of consciousness? These are non-trivial challenges that must be faced by the theory of conscious agents.

[p. 5 Objects of Consciousness]

However, he chooses to cast these questions aside in favour of an abstract mathematical formalism: 'But for the moment we will postpone them and develop the theory of conscious agents itself. [pp. 5-6]'

From the challenges described in this critical note, I find it difficult to see how, even in principle, Hoffman's mathematical constructs will ever answer these fundamental barriers. I would have liked to have seen Hoffman sketch out a conceptual framework that takes these problems seriously and that provides some heuristics for solving them instead of focusing on developing impoverished mathematical models that shed no light on the fundamental problems.

What is the mechanism behind a conscious agent's 'Decision'? How is this 'Decision' translated into an 'Action'? How does this 'Action' translate into a new 'Perception' had by another conscious agent? How is it that these conscious agents construct a reality that is not just a little off the mark, but is stupendously mistaken? How can they construct a reality in which only physical entities and forces existed for billions of years before the first onset of conscious beings? How can they construct a reality in which it appears that unconscious matter regularly determines the perceptual qualities, decisions and emotions of conscious beings? For what purpose this universal self-deception?

Hoffman shows no appetite at all for exploring these questions, favouring instead a mathematical formalism that obscures more than in clarifies. He seems content to give away for free the remarkable progress gained over the last couple of centuries in our understanding of consciousness' neuronal base for a supposition that throws up many more mysteries than it purports to solve.

A solution to the mind-body problem will require bold ideas if we are to finally marry seamlessly the two domains of enquiry: the physical and the mental—just as Newton brought into the one framework terrestrial and celestial motions and Einstein combined the absolute categories of space and time into the one space-time dimension. In that respect, I welcome Hoffman's innovative conjecture. As far as becoming a fruitful and ongoing research programme, as we have seen, it is yet to get some wind in its sails.


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