Planet of Zombies

The Fate of Mind in the Age of Turing

We are living today in the Age of Turing. Alan Turing was responsible for the theoretical work underlying contemporary computer science, but Turing’s work went far beyond the formal theory of the computer. Like Darwin, Turing’s thought ran ahead of the science he founded, and he openly speculated on the consequences of the future development of the computers that his theory made possible.

In his seminal paper “Computing Machinery and Intelligence” (the paper in which he introduced the “Turing Test,” which he called the “imitation game”) Turing began with the question, “Can machines think?” and went on to assert:

I believe that in about fifty years’ time it will be possible, to programme computers, with a storage capacity of about 10 to the 9th power, to make them play the imitation game so well that an average interrogator will not have more than 70 per cent chance of making the right identification after five minutes of questioning. The original question, “Can machines think?” I believe to be too meaningless to deserve discussion. Nevertheless I believe that at the end of the century the use of words and general educated opinion will have altered so much that one will be able to speak of machines thinking without expecting to be contradicted.
A. M. Turing, “Computing machinery and intelligence,” Mind, 1950, 59, 433–460.

Turing’s prediction hasn’t yet come to pass, but Turing was absolutely correct that one can speak of machines thinking without being contradicted. Indeed, Turing was more right than he could have guessed, as his idea that computers should be judged upon their performance — and even compared in the same way to human performance — rather than on a vague idea of thinking or consciousness, has become so commonplace that, if one maintains the contrary in public, one can expect to be contradicted.

Turing was, in respect to mind and consciousness, part of a larger intellectual movement that called into question “folk concepts,” which came to seem unacceptably vague and far too unwieldy in the light of the explanatory power of scientific concepts, the latter often constructed without reference to folk concepts, which came to be viewed as dispensable. Consciousness has been relegated to the status of a concept of “folk psychology” with no scientific basis.

While I am in sympathy with the need for rigorous scientific concepts, the eliminative approach to mind and consciousness has not resulted in greater explanatory power for scientific theories, but rather has reinforced an “explanatory gap” (a term made prominent by David Chalmers) that has resulted in a growing disconnect between the most rigorous sciences of human and animal behavior on the one hand, and on the other hand what we know to be true of our own experience, but which we cannot formulate or express in scientific terms. This is a problem. The perpetuation of this disconnect will only deepen our misunderstanding of ourselves and will continue to weaken the ability of science to explain anything that touches upon human experience. Moreover, this is not merely a human matter. We misunderstand the biosphere entire if we attempt to understand it while excluding the role of consciousness. More on this below.

Science has been misled in the study of consciousness by an analogy with the study of life. Life was once believed to be inexplicable in terms of pure science, and so there was a dispute between “mechanism” and “vitalism,” with the vitalists believing that there was some supernatural or other principle superadded to inanimate matter, and that possession of this distinctively vital element unaccountable in scientific terms distinguished the animate from the animate. Physics and chemistry alone could explain inanimate matter, but something more was needed, according to vitalism, to explain life. But with the progress of biology, vitalism was not so much refuted as made irrelevant. We now have a good grasp of biochemistry, and while a distinction is made between inorganic chemistry and biochemistry, it is all understood to be chemistry, and no vital spark is invoked to explain the chemistry distinctive of life.

Similarly, consciousness has been believed to be a “divine spark” within a human being that distinguishes a distinctively human perspective on the world, but consciousness “explained” in this way comes with considerable theological baggage, as explicitly theological terms like “soul” and “spirit” are typically used interchangeably with “consciousness” and “mind.” From a scientific perspective, this leaves much to be desired, and we could do much better. I agree with this. Turing’s imitation game seems to present us with an operational definition of consciousness that allows us to investigate mind and consciousness without reference to the theological baggage. There is much to gained by Turing’s approach, but the problem is that we have here no equivalent of chemistry — no underlying physical theory that could account for consciousness in the way that life is accounted for by biochemistry.

Part of the problem, and the problem that most interests me at present, is the anthropocentrism of both traditional theological formulations and contemporary scientific formulations. If we understand human consciousness not as an exception that definitively separates us from the rest of life on the planet, not as a naturalistic stand-in for a “divine spark” that would differentiate human beings from the “lower” animals, but as a distinctive development of consciousness already emergent in other forms preceding human beings, then we understand that human consciousness is continuous with other forms of consciousness in nature, and that, as conscious beings, we are part of something greater than ourselves, which is a biosphere in which consciousness is commonplace, like vision or flight.

There are naturalistic alternatives to an anthropocentric conception of consciousness, alternatives that place consciousness in the natural world, and which also have the virtue of avoiding the obvious problems of eliminativist of reductivist accounts of consciousness. I will consider the views of Antonio Damasio and John Searle. I do not fully agree with either of these authors, but I am in sympathy with these approaches, which seem to me to offer the possibility of further development, as fully scientific as Turing’s approach, but without the denial of consciousness as a distinctive constituent of the world.

Antonio R. Damasio in The Feeling of What Happens distinguished between core consciousness and extended consciousness. Core consciousness, he wrote:

“…provides the organism with a sense of self about one moment — now — and about one place — here. The scope of core consciousness is the here and now. Core consciousness does not illuminate the future, and the only past it vaguely lets us glimpse is that which occurred in the instant just before. There is no elsewhere, there is no before, there is no after.” (Antonio R. Damasio, The Feeling of What Happens: Body and Emotion in the Making of Consciousness, San Diego, New York, and London: Harcourt, Inc., 1999, p. 16)


“…core consciousness is a simple, biological phenomenon; it has one single level of organization; it is stable across the lifetime of the organism; it is not exclusively human; and it is not dependent on conventional memory, working memory, reasoning, or language.” (Loc. cit.)

The simplicity of core consciousness gives it a generality across organisms, and across the life span of a given organism; at any one time, it is always more or less the same. Extended consciousness, on the other hand, is both more complex and less robust, dependent upon an underlying core consciousness, but constructing from core consciousness what Damasio calls the “autobiographical self” in contradistinction to the ephemeral “core self” of core consciousness. Extended consciousness, Damasio says:

“…provides the organism with an elaborate sense of self — an identity and a person, you or me, no less — and places that person at a point in individual historical time, richly aware of the lived past and of the anticipated future, and keenly cognizant of the world beside it.” (Loc. cit.)


“…extended consciousness is a complex biological phenomenon; it has several levels of organization; and it evolves across the lifetime of the organism. Although I believe extended consciousness is also present in some nonhumans, at simple levels, it only attains its highest reaches in humans. It depends on conventional memory and working memory. When it attains its human peak, it is also enhanced by language.” (Loc. cit.)


“…extended consciousness is not an independent variety of consciousness: on the contrary, it is built on the foundation of core consciousness.” (Op. cit., p. 17)

One might add to this formulation by noting that, as extended consciousness is built on core consciousness, core consciousness is, in turn, built on the foundation of biological processes. I would probably describe consciousness in a somewhat different way, and would make different distinctions, but I find Damasio’s approach helpful, as he makes no attempt to explain away consciousness or to reduce it to something that it is not. Damasio seeks to describe and to explain consciousness as consciousness, and, moreover, sees consciousness as part of the natural world that is to be found embodied in many beings in addition to human beings, which latter constitutes, “…extended consciousness at its zenith.”

Damasio’s formulation of both core consciousness and extended consciousness as biological phenomena might be compared to what John Searle calls “biological naturalism.” What Searle, a philosopher, and Damasio, a neuroscientist, have in common is an interest in a naturalistic account of mind which is not eliminativist or reductivist. To this end, both emphasize the biological nature of consciousness. Searle has conveniently summarized his biological naturalism in six theses, as follows:

1. Consciousness consists of inner, qualitative, subjective states and processes. It has therefore a first-person ontology.
2. Because it has a first-person ontology, consciousness cannot be reduced to a third-person phenomena in the way that it is typical of other natural phenomena such as heat, liquidity, or solidity.
3. Consciousness is, above all, a biological phenomenon. Conscious processes are biological processes.
4. Conscious processes are caused by lower-level neuronal processes in the brain.
5. Consciousness consists of higher-level processes realized in the structure of the brain.
6. There is, as far as we know, no reason in principle why we could not build an artificial brain that also causes and realizes consciousness.
John R. Searle, Mind, Language and Society: Philosophy in the Real World, New York: Basic Books, 1999, p. 53

Searle’s formulations — again, as with Damasio, I would probably formulate these ideas a bit differently, but, on the whole, I am sympathetic to Searle’s approach — are a reaction against a reaction, i.e., against a reactionary theory of mind, which is the materialist theory of mind formulated in consciousness contradistinction to Cartesian dualism. Searle devotes a considerable portion of several books to the problems with this latter philosophy. I think the most important lesson to take away from Searle’s critique is not the technical dispute, but the thematic motives that underlie this philosophy of mind:

“How is it that so many philosophers and cognitive scientists can say so many things that, to me at least, seem obviously false? Extreme views in philosophy are almost never unintelligent; there are generally very deep and powerful reasons why they are held. I believe one of the unstated assumptions behind the current batch of views is that they represent the only scientifically acceptable alternatives to the antiscientism that went with traditional dualism, the belief in the immortality of the soul, spiritualism, and so on. Acceptance of the current views is motivated not so much by an independent conviction of their truth as by a terror of what are apparently the only alternatives.” (John R. Searle, The Rediscovery of the Mind, Cambridge and London: The MIT Press, Chap. 1)

The biologism of both Damasio and Searle make it possible not only to approach human consciousness scientifically, but also to place consciousness in nature — the alternatives being denying human consciousness or approaching it non-scientifically, and denying consciousness a place in nature. These alternatives have come to have a colorful representation in contemporary philosophy in the discussion of “philosophical zombies.” Philosophical zombies are beings like ourselves, but without consciousness. The question, then, is whether we can distinguish philosophical zombies from human beings in possession of consciousness. I hope that the reader will have noticed that, in the discussion of philosophical zombies we encounter another anthropocentric formulation. (I previously touched on some of the issues related to philosophical zombies in The Limitations of Human Consciousness, A Note on Soulless Zombies, and The Prodigal Philosopher Returns.)

The anthropocentrism of philosophical zombies can be amended by addressing philosophical zombies in a more comprehensive context, in which not only human beings have consciousness, but consciousness is common in the biosphere. Then the question becomes not, “can we distinguish between philosophical zombies and conscious human beings” but “can we distinguish between a biosphere in which consciousness plays a constitutive role and a biosphere in which consciousness is entirely absent”? This is potentially a very rich question, and I could unfold it over several volumes, rather than the several paragraphs that follow, which should be understood as only the barest sketch of the problem.

As I see it, reconstructing biosphere evolution should include the reconstruction, to the extent possible, of the evolution of consciousness as a component of the biosphere — when did it emerge? When did the structures upon which is supervenes emerge? How did consciousness evolve and adapt to changing selection pressures? How did consciousness radiate, and what forms has it taken? These questions are obviously entailed by biological naturalism. Presumably consciousness evolved gradually from earlier antecedents that were not consciousness. Damasio writes, “natural low-level attention precedes consciousness,” and, “consciousness and wakefulness, as well as consciousness and low-level attention, can be separated.” Again, I would formulate this a bit differently, but, in principle, states of a central nervous system prior to the emergence of consciousness would precede even rudimentary core consciousness. If these states of a central nervous system prior to consciousness include wakefulness and low-level attention, this would constitute a particular seriation of the evolution of consciousness.

Damasio calls human consciousness, “consciousness at its zenith,” and a naturalistic conception of consciousness recognizes this by placing this zenith of human consciousness at the far end of the continuum of consciousness, but still on a continuum that we share with other beings with which we share the biosphere. A human being is not only a being among beings, but also one biological being among other biological beings. Given Searle’s biological naturalism, our common biology — especially the common biology of our central nervous systems and brains — points to our being a conscious being among other conscious beings. This seems to be borne out in our ordinary experience, as we usually understand our experience. We interact with other conscious beings on the level of consciousness, but the quality of consciousness may differ among beings. Interacting with other beings on the level of awareness means that our relationships with other conscious beings are marked by mutual awareness: not only are we aware of the other, but the other is also aware of us.

Above and beyond mere consciousness is sentient consciousness, i.e., consciousness with an emotional element superadded. We interact with other sentient beings on the level of sentience, that is to say, on the level of feeling. Our relationships with other mammals, especially those we have made part of our civilization, like dogs and horses, are intimate, personal relationships, not mediated by intelligence, but mostly mediated by the emotional lives we share with our fellow mammals, endowed, like us, with a limbic system. We intuitively understand the interactions and group dynamics of other social species, because we are ourselves a social species, Even when the institutions of, for example, gorilla society or chimpanzee society, are radically different from the institutions of human society, we can recognize that these are societies, and we can sometimes recognize the different rules that govern these societies.

Even when human beings are absent from interactions in the biosphere, there are still interactions on the level of consciousness and sentience. When a bobcat chases a hare, both interact on the level of two core consciousnesses, and also, as mammals, they interact on a sentient level. The hare has that level of fear and panic possible for core consciousness, and the bobcat, no doubt, experiences the core consciousness equivalent of satisfaction if it catches the hare, and frustration if the hare escapes. Or when a herd of wild horses panics and stampedes, their common sentient response to some environmental stimulation provides the basis of their interaction as a herd species.

All of this can be denied, and we can study nature as though consciousness were no part of it. While I have assimilated the denial of consciousness in nature to anthropocentrism, many more assimilate the attribution of consciousness to other species as a form of anthropocentrism. Clearly, we need to better define anthropocentrism, where and how it misleads us, and where and how it better helps us to understand our fellow beings with which we share the biosphere. That position that identifies consciousness as peculiarly human and denies it to the rest of the biosphere is, in effect asserting that a biosphere of zombies is indistinguishable from a biosphere of consciousness beings; I can understand how this grows out of a legitimate concern to avoid anthropocentric extrapolations, but I can also recognize the violation of the Copernican principle in this position. The view that recognizes consciousness throughout the macroscopic biosphere can also be interpreted as consistent with avoiding anthropocentrism, but also is consonant with Copernicanism broadly construed.

To adopt an eliminativist or reductionist account of consciousness, i.e., to deny the reality of consciousness, is not only to deny consciousness to human beings (a denial that would be thoroughly anthropocentric), it is to deny consciousness to the whole of nature, to deny all consciousness of all kinds throughout nature. It is to assert that consciousness has no place in nature, and that a planet of zombies is indistinguishable from a planet of consciousness agents. Without consciousness, the world entire would be a planet of zombies.

To deny consciousness is to deny that there are any other species, or any other biospheres, in the universe in which consciousness plays a role. If we deny consciousness we also deny consciousness elsewhere in the universe, unless we insist that terrestrial life is the exception, and that, again, would be a non-Copernican position to take. To deny consciousness is to deny that consciousness will ever inhere in some non-biological substrate, i.e., it is to deny that machines will never become conscious, because there is no such thing as consciousness. To deny consciousness is to constitute in place of the biosphere we have, in which conscious interaction plays a prominent role in the lifeways of megafauna, a planet of zombies in which all of these apparent interactions are mere appearance, and the reality is non-conscious beings interacting mechanically and only mechanically. I am not presenting this as a moral horror, that we should avoid because it offends us, but as naturalistically — indeed, biologically — false. Our world is not a planet of zombies.

published at on August 21, 2016.