TRANSLATE THIS ARTICLE
Integral World: Exploring Therories of Everything
An independent forum for a critical discussion of the integral philosophy of Ken Wilber
Andrew P. Smith, who has a background in molecular biology, neuroscience and pharmacology, is author of e-books Worlds within Worlds and the novel Noosphere II, which are both available online. He has recently self-published "The Dimensions of Experience: A Natural History of Consciousness" (Xlibris, 2008).
Humans as History
A Comparative Review of
|12. Geopolitical states||MIND/CULTURE|
|10. Tribal metagroups|
|9. Animal social groups||LIFE|
|8. Complex multicellular organisms|
|7. Eukaryotic cells|
|6. Prokaryotic cells|
|3. Atomic nuclei|
|2. Nucleons: protons and neutrons|
|1. Fundamental quanta|
|CULTURAL||Society-based ecological communities||Human societies|
|Family-based ecological communities||Bird and mammal societies|
|Small ecological communities||Invertebrate food webs|
|Complex invertebrate societies||Ant colony|
|Simple invertebrate societies||Coral reef|
|BIOLOGICAL||Small world networks||Brain|
|Advanced cell networks||Neuronal ganglia|
|Simple cell networks||Motor unit|
|Advanced cell colonies||Multicellular tissues|
|Primitive cell colonies||Bacterial colonies|
|PHYSICAL||Metabolic systems||Citric acid cycle|
|Metabolic macromolecules||Enzymatic complexes|
|Small molecules||Amino acids|
Volk's stated approach is to identify examples of what he calls combogenesis, in which members of one form of existence associate into a new form (which I, following Wilber, usually refer to as holons; as an aside, I don't understand why he considers several other terms, but not that one, which seems to me the obvious one for a nested hierarchy or holarchy. However, I understand he has used that term in another book). We're in complete agreement here, not only in the general process, but that it involves changes in relations, or interactions. Combinations of atoms into molecules, molecules into cells, cells into organisms, and so on, involve new interactions among the original holons so that they can associate into something generally larger and more complex than themselves.
Comparing Volk's model with mine, though, some obvious differences stand out. Whereas he distinguishes only between molecules in general and cells, I distinguish several different kinds of molecules, including simple molecules (e.g., water, carbon dioxide); small molecules (amino acids, nucleotides); biological polymers (peptides, RNA); macromolecules (proteins, DNA); and macromolecular systems (Krebs cycle, electron transport chain). Likewise, while his model goes directly from cells to organisms, I identify several different kinds of multicellular organization, such as simple and complex cell units, tissues and organs.
There's no question, of course, that all these forms of organization not only exist, but were formed by some process of combogenesis. Why, then, doesn't Volk include them as levels in his model? In Chapter 8, he answers this question by arguing that they didn't appear in that order historically, but only somewhat later:
The body did not derive from a combogenesis of prior-existing heart, lungs, brains, liver. These organs evolved within the context of the evolution of very much simpler, multicellular whole creatures. Similarly, it seems like to me that some of the nested complexity of cells came about (“chemically evolved”?) within a context of something cell-like. 
I don't much disagree with this. I would say that some evolution of molecules occurred outside of cells (small molecules such as amino acids and nucleotides, some polymers, probably some simple macromolecular systems) and some evolution of multicellular organization occurred outside of organisms (as suggested by proto-organisms like Volvox and Dictyostelium, and very simple organisms like sponges). But probably much of this evolution only occurred within the next higher level, i.e., evolution of molecules within cells, evolution of multicellular organizations within organisms. And in fact, I don't regard either molecules or multicellular organizations as distinct levels, either, but rather as stages within levels. So in an important sense, we're in agreement as far as the classification of molecules and multicellular organizations goes.
That said, the concept of stages is a distinguishing feature of my model, and highlights a number of differences between that model and Volk's. I want to discuss these differences, and in particular, emphasize what I feel are some inconsistencies in his classification (which is nothing to be ashamed of; every model of holarchy I've ever seen, including my own, lacks perfect consistency. Life is messy!). He elevates to level-hood (if I may coin my own word) some forms of existenceprokaryotes and human societieswhich in my view, no more qualify for this than molecules and multicellular organizations. In criticizing Volk's model in this respect, I will to some extent be repeating criticisms I've made of Wilber's model, because like Volk, he has a broader view of levels than I have.
To be fair, I think many if not most of our differences boil down in large part to personal preferences. We don't disagree on what the facts are, to the extent they're known, and even in speculative areas, such as evolution of cells and evolution of the earliest multicellular organisms, I don't believe there are any substantial differences. So there isn't necessarily a right way and a wrong way to classify existence. We mostly differ I think in which characteristics we believe should take priority in a classification scheme. There's surely a subjective element involved in this.
Nevertheless, these differences do make a differenceto borrow a Batesonian termwhen seeking out general principles or what Volk calls recurring themes. For example, because he doesn't regard (most) molecules and multicellular organizations as constituting distinct levels, he doesn't focus on them when seeking out general principles or recurring themes. They do play an important role in his notion of alphakitsthe genetic code of course is embedded in molecules, and language in neural as well as social networksbut I think a great deal more can be said about relationships among these kinds of holons. In particular, there are some fairly significant analogies between some of these lower forms of existence and human societies. So after discussing what I believe are the most important differences in our views, I will look at some of their implications for recurring themes.
What's in a level?
Size isn't everything
Like Wilber and probably most other theorists, Volk distinguishes between prokaryotes and eukaryotes as different levels of existence. But eukaryotes did not evolve as a result of the combination of prokaryotes, in anything like the way that atoms combined into molecules, molecules combined into cells, or cells into organisms. One possible scenariothe one most consistent with Volk's point of viewis that one prokaryotic cell engulfed another, but this alone did not transform the engulfing cell into a eukaryote. Many other distinguishing features, particularly a nucleus containing chromosomes, had to follow, and we really don't even know how far along these processes may have progressed before the first cell was captured and incorporated. In any case, along the way, the original prokaryote was modified beyond recognition (until Lynn Margulis arrived), so just as is the case with molecules in cells and multicellular organization within organisms, a considerable amount of the evolution occurred within the newly emerging form of existence.
I do understand that Volk is aware of this, and even embraces it as a defining feature of what he calls a base level. Thus he makes an analogy between prokaryotic cells engulfing other prokaryotic cells and human agro groups incorporating animals and plants. He regards both prokaryotes and tribal metagroups as base levels, defined in large part by the emergence of the genome (what he calls the genetic alphakit) and language (linguistic alphakit), and in each case sees a similar dynamics playing out in the emergence of the following level:
Both second levels were created by the integration of different prior things:
Eukaryotic cells: from the combination and integration of two distinct kinds of prokaryotes, bacteria and archaea.
Agrovillages: from the combination and integration of earlier tribal metagroups…with plants and animals 
This is a very interesting analogy, and it's certainly worth pointing out and exploring, as Volk has done. But in the first place, the relationship is not unique. Individual humans, and many other organisms, also incorporate lower forms of life, mainly bacteria and particularly in the digestive system, which play a critical role in certain processes. Farming is also exhibited by a few other species, e.g., ants and aphids. Volk has strengthened the analogy by pointing out that in the case of eukaryotic and agro evolution, the lower form of life was used as an energy source, and that it ceded much of the control of its existence to the higher form. But one might say much the same about the human use of tools, a physical form of existence (but also involving plants, in the form of wood), which of course preceded farming. To me, all these are examples of opportunism, rife in evolution, and not the reflection of some general law of relations between levels.
Second, the transitions to eukaryotes and to tribal agro societies are not strictly analogous. According to current thinking, fully or nearly evolved eukaryotes did not engulf a lower form of life (if it turns out they did, that poses further problems for Volk's model, because it implies that this event was not a defining feature of eukaryotic evolution, but only something that occurred later, much as complex molecules and complex forms of multicellular organization evolved within cells and with organisms, respectively). Assuming one prokaryote incorporated another prokaryote, this is very different from a human society of any kind incorporating plants and animals.
Third, regardless of how valid one feels the analogy is, there are other reasons, which I regard as more compelling (this is an example of where personal preferences come in, I suppose), for rejecting the notions that a) prokaryotes and eukaryotes occupy distinct levels of existence, and b) either prokaryotes or eukaryotes are analogous to any human societies. With regard to the first point, the differences between prokaryotes and eukaryotes, while obviously of enormous evolutionary significance, are certainly no greater (I would say considerably less) than the differences between the simplest molecules and the most complex ones, or between individual cells and for example the brain. I would think anyone would also agree that the differences between prokaryotes and eukaryotes are not as great as those between ourselves and the simplest multicellular organisms, yet Volk actually implies that they are:
We can distinguish between changes (even large ones) within levels (worms becoming whales on the level of multicellularity) and transitions between levels (whales themselves as members of a social group on a new level) 
I'll say more later about the relationships of individuals to groups (an issue on whichaside from differences in classificationwe actually seem to be in large agreement), but for now I'll just point that both prokaryotic and eukaryotic cells are independently-existing forms of life capable of the fundamental properties of growth, self-maintenance and reproduction. Other than size and scale of energy production, the main significant difference is that (some) eukaryotic cells can associate with others of their kind in highly stable forms that created the potential to become a still newer form of life. This is basically the same distinction that exists between inert atoms like helium and reactive atoms like carbon, hydrogen, oxygen and nitrogen.
The description of prokaryotic and eukaryotic cells as independently existing forms of life capable of growth, self-maintenance and reproduction is also relevant to the question of the status of human (and animal) societies. These three properties are a defining feature of all cells and organismsusually pointed out on page 1 of any biology textbut not of animal or human societies; indeed, these properties are not completely manifested in any other forms of life at all. In the case of molecules and still lower forms of existence, we recognize that reproduction in particular only emerged at a certain level of complexity, so we can't expect lower levels to exhibit it. (That's why I regard atoms as fundamental holons, analogous to cells and organisms, though they of course don't reproduce). But higher levels it seems to me should be defined by holons that exhibit these properties, particularly reproduction, given how critical this process is to evolution (and as Volk himself points out, an important evolutionary principle is that major advances aren't discarded, but added to). The fact that societies don't exhibit them suggests to me that they should be treated differently.
Let's be clear about this. Human societies can grow and maintain themselves, of course, but these processes are vastly different from growth and homeostasis in cells and organisms, which are under strict control by internal factors. Cells and organisms grow to a particular size, or size range, and no further; societies don't. Cells and organisms develop certain reproducible features independently of their environment; societies for the most part don't. Cells and organisms create highly similar copies of themselves; societies don't. Wilber points to still other differences when he uses the term agency. Cells and organisms have agency; human and other animal societies don't, or at least not to nearly the same degree.
The Smith-Volk-Wilber triad
All this leads to the critical distinction between individual and social holons, which more than any other issue, illustrates the differences between my model, Volk's, and Wilber's. Wilber and I both make this distinctiondefining individual holons such as atoms, cells and organisms, and social holons such as societies of cells and organismsbut we treat them very differently. Wilber places social holons on a separate axis or line of development from individual holons, whereas I place them in the same line of development. In my view, individual holons develop directly into social holonsserially, so to speakwhich eventually develop into higher-level individual holons. There not only is no need for a separate axis, but I believe it's misleading, by implying that individual and social holons develop separately, though in parallel.
Volk differs from both Wilber and me by not making this individual-social distinction; that is, he treats societies as levels in the same conceptual sense as he treats cells or organisms as levels. In this sense, though, he's actually closer to Wilber than to me, because Wilber also regards societies as full-fledged levels, even if they develop somewhat separately. But Volk agrees with me that there is a single continuous line of development involving both types of holons, which is very much at odds with Wilber's view.
So each of the three of us agrees in one respect with one of the others, while disagreeing in another respect. But here's where it gets tricky, and personal preferences come into play. I have just criticized Wilber by claiming that individual and social holons develop in series, rather than in parallel. But that's not entirely true. As I will discuss later, there's a lot of evidence, which Volk also cites, that development in both individuals and societies can proceed simultaneously, in a coupled fashion. This is well-established for the human brain and human societies; the so-called social brain hypothesis explicitly says that evolution of each was dependent on the other. And though we have less direct evidence, probably a similar relationship occurred during evolution of multicellular organisms, between the genome of eukaryotic cells, and the multicellular organizations these cells were forming.
Wilber can appeal to such relationships to support his model of evolution in parallel. Cells and organisms evolve at the same time as their societies do, with each affecting the other. A major problem (not the only one) with his “separate but equal” view is that social holons and their component individual holons are not equal. Though Volk may not use these two terms, he clearly agrees with me here. Thus human societies are higher, more evolved, than individual humans, by any reasonable understanding of the term. As he emphasizes, they're formed by combogenesis of humans, just as cells are formed by combogenesis of atoms, organisms by combogenesis of cells, and so on. They're more complex, including not only all individual humans but an astronomical number of interactions among them. And they have emergent properties; even small tribes, let alone complex modern civilization, can accomplish things no individual could.
So while individual and social holons may develop at the same time, that doesn't preclude understanding that development is taking place on a single axis. It just means that evolutionary change can occur at multiple positions on the axis, at the same time. So our common position on this issue is certainly consistent with coupled evolution, and has the immense advantage of emphasizing that not only does the social develop from the individual, but the individual develops from the social. However, I think viewing societies as stages within a level is preferable, because rather than proposing that evolution is occurring on two different levels simultaneouslyas Volk in effect must doI'm proposing that evolution is occurring simultaneously in different stages of a single level. In my model, evolution of one level is pretty much finished by the time evolution of the next level begins. In Volk's model, that is definitely not the case.
To summarize my differences with Volk on this issue, I don't think that societies should be considered a separate level of existence in the same way that cells and organisms are. In my view, societies exist independently only because the potential higher level that could evolve and integrate them has not yet emerged. In other words, I view societies much like primordial molecules and multicellular organizations, which also must have been independent and capable of some growth and self-maintenance prior to the evolution of cells and organisms. This is obviously speculative, and Volk may not agree with it (though his discussion in the Epilogue suggests he's sympathetic to it), but surely everyone must accept that societies are very different in kind from either cells or organisms. For me, not incorporating this point explicitly into any model is too high a price to pay for whatever other benefits the model may provide.
What's in a name?
Finally, another inconsistency, in my view, emerges in Volk's treatment of molecules vs. forms of multicellular organization. He doesn't distinguish any levels of the latter, because he doesn't see any evidence that they existed independently prior to the evolution of organisms. But in fact, as seen in proto-organisms or rudimentary organisms I mentioned earlier, it's abundantly obvious that some multicellular evolution had to occur before genuine organisms evolved. I think his reply would be that there might have been such independently existing precursors to tissues and possibly organs, but lacking any strong evidence, he feels that at least for the time being it would be better not to include such a level. Fair enough. But if that's the case, why include molecules, either?
What I'm getting at is that what makes both molecules and multicellular organizations problematic as levels similar in kind to cells and organismsin addition to the fact, noted earlier, that they don't exhibit growth, self-maintenance and reproductionis that both are almost entirely non-existent outside of cells and organisms, respectively. In fact, the former condition implies the latter. Other than what I call simple molecules, consisting of only a very small number of atoms (or larger aggregates of a single atom, exemplified by minerals, which exhibit no new kinds of interactions, and hence no emergent properties), almost all molecules existing today are associated with cells and organisms. Volk clearly recognize this, yet he still treats molecules differently from multicellular organizations. It seems to me that if one is going to pass over multicellular organizations as a distinct level of existencenot because these organizations didn't evolve, but because of a paucity of evidence beyond speculation that they evolved outside of organismsone should do the same with molecules.
I think the problem here may be terminology. It just happens that we call all forms of existence that consist of interacting atomswhether they be extremely small and simple, like water and carbon dioxide, or relatively enormous and complex, like proteins and DNAby the same name: molecules. In contrast, we don't call all forms of interacting eukaryotic cells by the same name. We call slime molds and sponges organisms or proto-organisms, whereas we refer to neural networks in brains as tissues. But the relationships between the latter mirror those that exist between simple and complex molecules. So names aside, I see no logical basis for treating these relationships differently.
Stages as dimensions
Now I turn to a discussion of general principles or recurring themes. I very much agree with Volk that having created some kind of model, we want to look for such themes, not just as a way of adding details to the model, but as possibly useful in predicting the existence of new phenomena, or in gaining new insights into already known phenomena. These themes, though, obviously depend to a large extent on how we define levels, which is to say, what we regard as the kind of relationships that result in the emergence of a new level.
As I've just discussed, my model differs from Volk'sand from Wilber's, and from most other models of this kind I'm aware ofin that it proposes distinct stages within levels. Thus I identify many different kinds of molecules, while Volk and Wilber group them all in one class. I identify many different kinds of multicellular organizations, while both Volk and Wilber ignore them as far as classification of levels occurs. Volk does define three major dynamical realms, which have some similarity to my view of three major levels, but in his model, if I understand it correctly, all the twelve levels are treated more or less equally. The realms simply refer to groups of levels where new themes emerge.
In contrast, my stages are different in kind from levels; they are smaller, less complex transitions, so to speak, which occur on the way to the creation of a new level. Though as I just stated this is also a major difference between my model and Wilber's, he did later on adopt the notion of tiers, which have somewhat the same relationship to levels as in my model levels have to stages. I mention this because I think sooner or later theorists have to concede that a single term, like level, is not sufficient to describe evolution, even in very broad outlines. There are extremely important transitions that occur within levels as well.
Volk is obviously aware of this. Thus in his discussion of alphakits, the genetic one that led to a great variety of proteins, and ultimately provided the basis for Darwinian evolution, and the linguistic one that is fundamental to cultural evolution, he notes how these can be built up hierarchically:
Things in biology and culture, with their unique, innovative alphakits, have a series of higher-order nestings greater than even the cornucopia sets of proteins in the living cells and words in the cultural webs of “we”. These higher-order networks derive from the interactions of the members of the cornucopia sets… The members of the respective cornucopia sets (proteins, [genes], words) of both genetic and linguistic alphakits are involved in higher-scale networks (protein [gene] networks, sentences, etc.) vital to the inner workings of even larger respective things (prokaryotic cells, tribal metagroups) where those alphakits began. 
I couldn't agree more. But why not make these relationships more explicit? This is what I have tried to do by identifying stages within levels. Thus my stages within a cell include proteins and protein networks, and my stages in higher levels, while not corresponding with linguistic structures (we don't really know enough about their correlations to make this kind of connection), certainly reflect the same kind of nesting process. In the discussion that follows, I will describe some general themes or principles I see emerging from this view.
Infinity and orthogonality
I begin by noting that Volk describes his model as logical, but not mathematical. My model is mathematical as well as logical, as it's based on dimensions. I initially refer to these dimensions as natural, to distinguish them from conventionally-understood mathematical dimensions, which have a relationship of infinity (line vs. point, plane vs. line, etc.). One feature of natural dimensions is the relationship of not infinity, but a large though finite number. Thus an organism has not an infinite number of cells, but a very large number of them, cells in turn contain a very large number of molecules, and molecules in turn may be composed of a very large number of atoms.
But it's more than just the relationship of many to few, and this is the key to how I define stages within levels. Compare a metabolic pathway, such as the Krebs cycle or the electron transport system within a cell, to a single atom. This metabolic system has a very large number of atoms, but they're arranged in several fairly discrete stages. Atoms combine into amino acids; amino acids combine into peptides; peptides combine into proteins; proteins combine into a metabolic system. One important rationale for seeing these different types of molecules as distinct stages is that each molecule is synthesized by combining the molecules of the previous stage. Peptides can only be synthesized by combining amino acids, not directly from simpler precursors. Complex proteins are created by combining several peptides. Metabolic systems combine numerous proteins. Each step has to occur in order for the subsequent step to be possible; there's no skipping. So a peptide is not just a large number of atoms. It's a large number of amino acids, each of which in turn contains many atoms. And so on.
Now here's the key point. Each of these steps potentially creates a new dimension; my claim is that a hierarchy, at least any well-developed natural one, is by definition a series of dimensions. If this point isn't generally appreciated, it's because we usually associate dimensions with mathematical relationships involving infinity. As I just noted, a line is composed of an infinite number of points; a plane of an infinite number of lines; and a three dimensional object of an infinite number of planes. But note that while the three dimensional object could also be said to combine an infinite number of points, its three dimensions result not from this single relationship of infinity, but from multiple relationships, from point to line to plane to three dimensions. In other words, the key factor in creating new dimensions is not infinity, but another kind of relationship, known as orthogonality.
This term is used in many different fields, and has as many different meanings, but I believe the one most relevant to understanding hierarchy comes from statistics: two independent variables are said to be orthogonal if they have no correlation with each other. This is basically the sense in which it's used in other fields as well. In mathematics, two lines are orthogonal if they're perpendicular, which is to say their directions in vector space are uncorrelated. In computer science, language features are orthogonal if they can be combined in any arbitrary way; in other words, their meanings are uncorrelated. In taxonomy, a classification is orthogonal if no individual is the member of more than one group; that is, membership is uncorrelated.
The same principle applies to stages in a hierarchy. Consider the difference between an amino acid and a peptide (or a nucleotide base and a nucleic acid molecule). Both amino acids and nucleotides are composed of atoms that are joined by covalent bonds. Their new, emergent propertiesrelative to those of the individual atoms they're composed ofresult from the relationships expressed by these bonds. I will discuss an example of such a property shortly.
When amino acids join into a peptide, or nucleotides into nucleic acids, covalent bonds are also involved. But the new, emergent properties of these biological polymers don't result from such bonds. They result from other types of bondse.g., hydrogen bonds, electrostatic bonds and hydrophobic interactionsand most critically, the net effect is recognition not of individual atoms but of groups of atoms, or molecules. When a peptide folds into a biologically active conformation, certain amino acid molecules recognize and interact with other amino acids. When two nucleic acids combine into a duplex, each nucleotide base recognizes a complementary base.
This kind of interaction creates a second dimension because it's largely independent of, or uncorrelated with, covalent bonding. The covalent bonds formed by interaction of the individual atoms of each amino acid are preserved, even as amino acids themselves interact as groups of atoms. This is the essence of orthogonality, which makes it possible for a new dimension to emerge.
What kinds of properties result from the emergence of this new dimension? One of the properties of an amino acid, and many other small biological molecules, is the ability to sense and stabilize (buffer) the pH, or hydrogen ion concentration, of its environment, by virtue of having two or more ionizable atoms. This property, which is a critical to maintaining a homeostatic milieu within cells, is a form of one-dimensional interaction, or intensity discrimination; some parameter (in this case, pH) is evaluated on a simple linear scale. All amino acids, regardless of differences in their specific structure, exhibit this general property (as do nucleotides).
A peptide, in contrast, can recognize two dimensions, such as a surface. In fact, peptides frequently fold into essentially two-dimensional forms such as a-helices and b-sheets, and this kind of conformation is known as secondary structure, to distinguish it from primary structure, which is simply the linear sequence of amino acids in the peptide (some nucleic acids, such as transfer RNA, also form secondary structure). Tertiary structure, exhibited by complex proteins, is associated with three-dimensional conformations. Peptides and proteins not only embody two- or three-dimensional forms, respectively, but are capable of recognizing such forms in other molecules. These properties are the key to the interactions of substrates with enzymes, ligands with receptors, and other metabolic processes within all cells.
From the physical to the perceptual
Discussing dimensions in terms of existence as simple as biological molecules may make them seem abstract and academic. But the same principles apply to higher forms of life, and in my view, account for our own experience of space and time. Let me quote at length from the first chapter of my book The Dimensions of Experience (DE):
So a central claim I will defend in this book is that conscious experience of the world evolved in fairly discrete stages, each characterized by a certain degree of dimensionality, and that each stage was associated with a certain degree of complexity. Indeed, as is often the case with evolutionary stages, we can see all of them played out within our own species. Consider vision, one of our most highly developed means of experiencing the world. Human vision begins with light energy striking the retina. At this stage, our experience of the world (if we were aware of it) is largely one-dimensional. The light sensitive cells in the retina, rods and cones, are sensitive to intensity of light, and that is the information they send to the brain.
It is only laterin an evolutionarily higher part of the nervous system, the visual cortexthat this information about light intensity becomes transformed into such experience as the orientation of lines or edges. This kind of information, I will discuss later, is a key feature of two-dimensional experience, the ability to recognize and distinguish surfaces. Further processing in the visual cortex, requiring still more complex portions of the nervous system, results in our ability to experience three dimensions of space. Some experience of time is also elaborated in the visual cortex, because cells in certain parts of this brain region are sensitive to motion, but our highly developed experience of timeallowing us, for example, to form enduring mental representations of objects in the environmentrequires further processing in still more complex regions of the brain, areas outside of the visual cortex that relatively few other organisms have.
The example of visual experience not only illustrates how our multi-dimensional view of the world is built up through information processing in increasingly more complex neural structures, but illuminates a key relationship of these structures to each other: they are hierarchical…For example, cells in the V1 region of the visual cortex, many of which respond to edges, receive (indirectly, through intervening neurons in the visual pathway) inputs from a small group of cells in the retina (Hubel and Wiesel 1959, 1962; Chapman et al. 1991). A single cell in V1 thus has access to all of the information contained in an entire group of cells at the level of the retina. Likewise, it is now believed that cells in hierarchically higher areas of the visual cortex, as well as other areas that obtain information from the visual cortex, elaborate three dimensional experience by integrating informational inputs from many of the edge cells (Stringer and Rolls 2002; Tsutsui et al. 2002; Sereno et al. 2002; Welchman et al 2005; Grossberg et al. 2007). Regions of the brain where our extended sense of time emerges lie outside the visual system, but receive inputs from large numbers of cells that are involved in processing of spatial information (Baker et al. 2001; Baird et al. 2002).
This example illustrates that hierarchical arrangement is associated not simply with physical dimensions, in the natural sense, but also perceptual dimensions, in the mathematical sense. The reason that natural dimensions can be converted into mathematical ones is because, as I noted earlier, the key feature of dimensions is not infinity but orthogonality. Vision begins with an infinite relationship, in the form of a scale of light intensity. This is quite analogous, on the biological level, to the intensity discrimination performed by an amino acid molecule; light intensity can be understood mathematically as a line, with the retinal cells determining where on the line the stimulus is located. Once one has an infinity of this sort, orthogonality ensures that further dimensions result in further infinities. All the work, speaking very loosely, is done by the initial infinity.
Members with benefits
So hierarchies generate new dimensions, which in my model are the key to understanding many new properties, including the perception of an increasing number of dimensions of space and time. This is not the only way to understand how hierarchy creates new properties. One can also describe the process in terms of an increase in complexity; higher stages are more complex than lower stages, and of course higher levels are more complex than lower levels.
But I regard the existence of such dimensions as clearly a recurring theme, and speaking more broadly, understanding levels as built up in hierarchical stages makes it easier to identify further themes, since we can define, fairly precisely, corresponding stages on different levels. In other words, stages tell us where to look for recurring themes. We may also obtain more insight into themes already identified. Consider Volk's observation that:
The start of full-on cultural evolution consisted of two, coupled scales of evolutionary dynamics: cognitive within individuals and social among members of tribal metagroups. 
Again, I agree completely. This is basically a restatement of the well known social brain hypothesis, with the understanding that it's not just social evolution driving evolution of the brain, but the two evolving together. As I discussed earlier, this is the kind of relationship that has led Wilber to regard evolution of the individual and the social occurring on two parallel tracks. As I pointed out at the time, this isn't necessary, but let's flesh this out further in terms of stages.
The previous discussion implies that higher-dimensional experience is not an individual but rather a social property. Complex molecules within cells are social holons, in my model. Neural networks in the brain are also social holons. How then can individuals like ourselves experience these higher dimensions?
The answer is because we are members of still higher-level social holons, complex modern societies. These societies, just like complex molecules within cells, and complex networks within the brain, generate higher dimensional experience. The key to this experience largely lies in language. I have discussed this at length before (DE), and will not repeat that here, but will just point out that language is a social property, one that can only be created and have meaning within a group of individuals, and that it presupposes an experience of not only three dimensional space, but also of dimensions of time, so that the referents of words have an existence beyond our immediate experience of them.
In this view, the neural networks in the brain don't directly generate the dimensions that we experience; rather, they allow us to participate in the social networks where this experience is generated. The hierarchical chain of neuronal networks that a light stimulus travels up when it enters the brain was formed during evolution because it allowed us to interact with large numbers of other organisms (initially), eventually humans, in complex ways. It's this interaction that is at the basis of our dimensional experience.
Note that this view also implies that similar relationships hold on lower levels of existence. There are neurons in the brain that sense higher dimensional activity by virtue of being members of the higher-dimensional neural networks. There are atoms in metabolic systems that experience sense higher dimensional activity by virtue of being members of higher-dimensional molecular networks.
Volk summarizes the nested relationships of genetic and linguistic alphakits with his statement:
Language in culture is a multi-scaled metabolism, like nested networks of protein systems in a cell. 
In fact, we can say something more about this “multi-scaled metabolism” as it exists in cells, in brains, and in culture. Complex networks at all three of these levels have in common a similar type of organization known as scale-free (Barabasi 2002, 2003). A scale-free network is governed by a power law, that is, there is an inverse correlation between the frequency of a particular node and the number of links or interactions it has with other nodes. In other words, there are a very small number of highly-connected nodes, and most of the interactions of other nodes go through these hubs or “stars” (the basis of the well-known saying, six degrees of separation). A large body of research has shown that scale-free organization predominates in metabolic networks in cells (Jeong et al. 2000; Wuchty 2001; Yook et al. 2004); in neural networks in the human brain (Hilgetag et al. 2000; Sporns and Zwi 2004; Achard et al. 2006); and in social networks of human societies (Yook et al. 2002; Ebel et al. 2002; Bilke and Peterson 2001; Davidsen et al. 2002). In my model, all of these represent the highest-dimensional stages on their respective level of existence (physical, biological, cultural).
The genome (including not just DNA, but the wide variety of molecular systems required to transcribe and translate the genetic code) is the highest dimensional stage within the cell. It contains the information needed both to control cell growth and maintenance, and to reproduce the cell. In the same way, the brain is the highest dimensional system within the organism. It contains information needed to control all the major processes of the body, and also for reproducing the organism. Human culture, which I regard as the evolving brain on a higher level of existence, contains the information needed to control the processes of this higher level of existence, and hypothetically, might some day be used to reproduce it (colonizing another planet, for example).
This understanding not only precisely locates the genetic and linguistic alphakits within their respective levels, but suggests the existence of a third alphakit: neural. I think Volk is pointing to this when he says, “There are neural and behavioral operations that contain correspondences to the trio of logical strands of propagation, variation and selection.”  Like both genes and human societies, neural networks employ a code, though this is poorly understood. We have known for a long time that neurons communicate through spikes or action potentialslocal areas of depolarized surface membrane that are transmitted very rapidly down the axonand which may, upon reaching a synapse, transmit electrical activity to an adjacent neuron. What is less well appreciated is how information is carried in trains of spikes, which can be characterized by such features as their amplitude, frequency and regularity. But there clearly is a neural code, which must have a similar function on its level to that of the genome and human language.
Looking up and looking down
Since I've brought Wilber into the comparison, I would be remiss in not discussing his other main distinction, between exteriors and interiors. In his model, there are not only both individual and social holons, but each has both an exterior and interior. This is how he generates four axes or scales of development.
The concept of interiors is Wilber's response to scientific materialism, which he ridicules as “flatland”. In his view, there's far more to existence than atoms, molecules, cells, organisms and societies, as they are understood by science. There are mental phenomena, which are more generally referred to as interior because we can't actually see them as we can see the exterior holons. Science doesn't deny the existence of mind, or consciousness, of course, but in the materialistic view that currently holds sway among most scientists, these phenomena in some manner emerge from (or in the view of the more hard core scientists and philosophers, are identical to) neural processes in the brain. So most holarchical models, while focusing on the exteriors, don't of course deny the existence of mind or consciousness. As Volk puts it, “Terms such as mind, consciousness, value, mental time travel, equality, obligations and reputation come into play in these [cultural] systems.” 
I agree with this conventional scientific view to a large extent, but I have some sympathy with Wilber as well. There is an aspect of mind or consciousnesswhat philosopher David Chalmers (1996) calls the hard problemthat defies attempts at explanation in terms of material processes. This problem of course has stumped philosophers for centuries, leading to a long-running argument between materialism and dualism. Without adding to this discussion, I'll just say I don't believe we can point to human brains, interacting in human cultures, and say, consciousness can be completely accounted for by these processes, even if we don't yet understand how.
On the other hand, I believe Wilber greatly underestimates the degree to which mental phenomena can emerge from brains and societies. We know that thoughts, ideas, values, feelings, and so on, are closely associated with certain areas in the brain, to the point where in theory (which is already approaching practice) we can identify certain patterns of neural activity as associated with specific types of mental activity. Chalmers (2000) refers to these patterns as “neural correlates of consciousness”, but when he uses consciousness in this sense, he's referring to what he calls the “soft” (still very difficult, but in principle tractable) problems of mental function, as opposed to the hard problem of raw experience or qualia. If we were able to create an unconscious robot or other hypothetical form of existence (which cognitive philosophers refer to as a zombie) that could perform behaviorally just like a real human being, it would be because we had solved all the soft problems of consciousness.
I'm largely in agreement with Chalmers on this distinction, except that, as I discussed earlier, I believe social interactions are what actually generate our mental functions. Neural processes in the brain allow us to access these social interactions, so while these neural processes correlate with mental functions, the relationship is somewhat indirect. This view may seem a little strange, and at odds with the way most scientists (and cognitive philosophers, like Chalmers) view the relationship of the brain to mind, but it actually allows a more unified view of brain function, one that allows us to jettison the concept of distinct interior holons and describe mind (in the functional sense) in terms of physical stages.
Let's begin by redefining exteriors and interiors in terms of a commonly made distinction in philosophy between public and private experience. Public experience is that which everyone shares, and is a critical process in the advancement of science. We all agree that certain objects and processes exist in the worldrocks and trees, animals moving, people talking, and even molecules and microscopic organisms, and distant stars, and on and onbecause they appear consistently under certain conditions that we can specify to each other. This is the external world, what science calls objective reality. Many philosophers might argue that there is a large degree of subjectivity in this reality, but we don't have to be concerned with that here. The fact that science “works”that we can create airplanes, computers, successful drugs, and so onverifies that there is something “out there” that all of us interact with.
Private experience refers to that which we can't directly share: our thoughts, feelings, mental images, memories, and so on. While we can describe these to others, these descriptions are necessarily much less precise. I can tell you what I'm thinking or feeling, but you can't experience my thoughts or feelings in the same way that way that you can experience my view of say, a house or a car or a tree. This is the interior world, and is subjective; it generally has no reality to anyone other than the individual experiencing it.
In my model, both types of experience result from observing some aspect of the world. The distinction between external and internal reflects where we stand in relationship to that aspect. We experience exteriors when we look down in the holarchy, so to speakat lower forms of existence, everything from rocks and trees to animal and human bodies and so on. We see them as objects, distinct from ourselves, and because they are distinct from ourselves, our experience of them is shared. We see basically the same thing.
In contrast, we experience interiors when we look upwards, at human societies, which are higher stages on our own level. We see them as subjects, an extended part of ourselves. Because they include ourselves, this experience is not shared. We're not simply observing social interactions, but social interactions as they include us.
So this is one way in which I differ from Wilber on the issue of interiors. I don't require a separate scale for mental phenomena, because I view them as resulting from the same scale that organizes physical or material phenomena. The distinction between exterior and interior translates into the distinction between below and above. This is largely compatible with the conventional scientific view, with the understanding that these mental phenomena originate from human societies, though they're accessed through human brains.
However, after accounting for mental phenomenaChalmer's soft problem or problemswe're still left with the hard problem, the raw experience or qualia of consciousness. Explaining mental function does not explain our experience of this function. Chalmers's own solution to this problem is a form of what philosophers call property dualism, or in common parlance, panpsychism. He believe that all forms of existence have some degree of consciousness, that consciousness is in fact an intrinsic property of matter, somewhat like, say, mass or charge.
Wilber has expressed a very similar view, one I'm quite sympathetic to. Panpsychism is regarded by probably most scientists and philosophers as absurd, because it seems to imply that very simple forms of existenceone-celled organisms, even molecules and atomsare conscious in somewhat the same sense that we are. But all that panpsychism really requires is that consciousness can range over an extremely broad level of intensity, much as, for example, light can. From the point of view of typical daylight intensity on earth, a single photon is so dim that it appears to emit no light at all. Yet there is in fact a continuous scale, so that given enough photons, a recognizably intense amount of light emerges.
In somewhat the same sense, it seems to me that consciousness, starting from a level or degree that from our normal point of view would represent a total absence of this phenomenon, can evolve to the level we're familiar with in ourselves (and still higher levels that are beyond the scope of this discussion, but which have obvious relevance to predictions of future evolution). Volk's concept of combogenesis should help us appreciate not only this possibility, but why it means that a separate scale for consciousness is unnecessary. As atoms combine into molecules, molecules into cells, cells into organisms, and so on, resulting in increasingly larger and more complex physical systems, any postulated consciousness intrinsically associated with these holons also would become more complex, which means not only capable of increasingly more sophisticated functions, but also of greater intensity, i.e., level of awareness.
Evolution in stages
Any holarchical model is a description of how matter and life have evolved, and so must reflect the outcome of evolutionary processes. The two most widely recognized of these processes are Darwinian evolution and cultural evolution. Volk notes the role of genetic and linguistic alphakits, respectively, in these processes, and identifies three general elementspropagation, variation and selectionthat are common to both kinds of evolution. These are all very important points that help explain how evolution has produced the holarchy.
But some theorists argue that there are other evolutionary processes. In Evolution in Four Dimensions, which Volk lists in his bibliography, Jablonka (Jablonka and Lamb 2005) identifies, in addition to Darwinism and cultural evolution, epigenetic and behavioral evolution. Epigenetics refers to heritable processes within the cell that are not the result of mutations or other changes in the genetic code. The most oft-cited example is probably DNA methylation, modifications of DNA that can turn certain genes on or off, but Jablonka argues for the existence of several other processes. Behavioral evolution might be thought of as cultural evolution-lite, a process by which certain forms of behavior are passed on by example in animal societies (and probably also among pre-linguistic children). It's like cultural evolution, except that transmission doesn't occur through language or symbols, but by imitating some form of behavior.
Understanding that evolution of cells, organisms and societies occurs through stages allows us not only to classify these evolutionary processes according to where on a level of existence they occur, but to identify additional processes (see table). Beginning with cultural evolution, we all understand that this occurs among human societies, which in my model is the highest stage on the cultural level. Individuals express and communicate certain ideas or forms of behavior through language. It's important to understand that the use of language means that cultural evolution is basically a process by which certain patterns of interactions between individuals are selected. This contrasts with Darwinian evolution, where the selection process acts on individuals, though eventually populations are affected.
|Level||5D stage||4D stage|
|Cultural||Cultural evolution||Behavioral evolution|
|Biological||Neural plasticity||Synaptic plasticity|
|Physical||Self-sustaining metabolic loops||Conformational change|
Cultural evolution has an analog on the highest stages of the biological level, that is, among networks in the brain. It takes the form of neural plasticity, the ability of neural connections to rewire under certain conditions. Just as certain patterns of interactions among individuals in societies are propagated and selected for because of some benefit they provide, certain interactions among neurons in the brain are also propagated and selected for. Neural plasticity probably underlies a great deal of cultural evolution, but it's not confined to our species. Many studies of animals in the laboratory have demonstrated that the process is critical to early development, and learning in general. It's also involved in the brain's response to certain kinds of injuries (Merzenich et al. 1983, 1984).
On a still lower level, the physical, a process analogous to cultural evolution is self-sustaining metabolic loops, one of the epigenetic processes discussed by Jablonka. Self-sustaining metabolic loops are enzymatic networks in which the products of some enzymes may serve as substrates, stimulators or inhibitors of other enzymes in the network. As a result of these interactions, these networks can exist in a very large number of different statesdepending on which enzymes are active or inactive, and to what degreeand one particular state may be selected for if it has a beneficial effect on the cell. So again, what is selected is a certain pattern of interaction among lower holons.
While neural plasticity and self-sustaining metabolic loops are phenomena known to exist, neither process has actually been demonstrated to play a role during evolution. That is, there is no evidence I'm aware of that either of these processes was critical to the emergence of new adaptations. But recognizing that these processes are highly analogous to cultural evolutiondiffering from it mostly by occurring on a different level of existenceraises this possibility, and thus identifies a potentially fruitful area for future research.
Now let's consider behavioral evolution. As an example of this, Jablonka notes that some species of birds will develop a new, beneficial form of behavior, and this is transmitted to their young by example; the young birds learn by imitation. Young children, of course, are masters at this. Because birds and other non-human animals do not communicate through language or symbols (nor do pre-linguistic children), this kind of evolution in my model occurs on a lower stage than cultural evolution. Selection still acts upon a pattern of social interactions, but these interactions are much less complex than those mediated by language.
On the biological level, the analog of behavioral evolution is synaptic plasticity; individual neurons transmit changes to other neurons they are connected with. This is a well-established phenomenon that occurs learning and other short-term changes of behavior (Malenka 2002). For example, if a particular synapse between two neurons is used frequently, it may become strengthened, so that a less intense stimulus is required for one neuron to communicate to the other.
On the physical level, an analog of behavioral evolution is conformational change, another form of epigenetics. A general example of this is illustrated when a protein molecule, which has a certain three-dimensional conformation, induces a similar conformation in other proteins. Prions, the cause of disorders such as mad cow disease, are the best known example, but some evidence suggests that prion-like proteins are found in microorganisms such as yeast, where they may perform a normal physiological function (Serio and Lindquist 2000).
As is the case with neural plasticity and metabolic loops, phenomena like synaptic plasticity and protein conformational change have not been shown to have played an evolutionary role. Again, though, their resemblance to a higher-level process for which there is somewhat better evidence for evolutionary relevance suggests the possibility. Understanding that stages on any particular level of existence have equivalents on other levels guides us to these processes, potentially greatly expanding our view of evolutionary change.
In this discussion of Volk's model, I've emphasized differences with my own model, because these differences help highlight key features in both models, and may point to ways to improve them. But as I said at the outset, there are large areas of agreement between us. These include the single developmental scale, the role of combogenesis, distinctive realms, coupled evolution, analogies between phenomena on different levels, relevance to future evolutionary change. Most of the scientific community accepts the notion of levels of existence in a very general sense, in that new forms of life emerge that can't be completely reduced to what came before them. I hope Volk's book will encourage more scientists to consider these levels in more detail, as a valuable framework for future research.
 Quoted by Visser (2018)
 Quotes from Q2C are referenced by their kindle location.
 There is much more to my criticism of Wilber than I've discussed here. For example, while he includes societies of cells in his model, he only recognizes relatively undeveloped ones, such as bacterial colonies. He does not consider the much more complex cell societies found within organisms, and in the same way, he ignores complex molecules within cells. So the social holons he recognizes at these lower levels are not at all analogous to human societies. Even further, Wilber's distinction between individual and social has not been consistent. At various times, he has proposed that a) individual and social holons are distinct from each other; b) every holon has both an individual and a social aspect; and c) both a) and b) are true. I have discussed the logical and empirical flaws in this view at length (Smith 2002; 2006a,b).
 As noted in endnote 3, Wilber does not recognize multicellular organizations within organisms as societies. Thus his model is unable to address the full extent of coupled evolution between cells and their societies, most of which occurred within organisms, not in relatively simple bacterial or eukaryotic cell colonies. For the same reason, his understanding of molecules fails to incorporate the extensive coupling between their evolution and that of cells.
 Thus the formation of all naturally-occurring atoms was complete at the time that cells began to evolve, and evolution of modern eukaryotic cells was mostly complete at the time of the emergence of fairly simple multicellular organisms. If a new, higher level of existence is emerging on earth, it comes as the evolution of organisms is apparently complete. In fact, this is another way of defining or distinguishing levels, or more precisely, distinguishing the fundamental holons which begin the evolution of a new level. A fundamental holon is one which has completed its evolution prior to the emergence of the succeeding higher fundamental holon. In contrast, evolution of molecules was not complete prior to the emergence of cells, nor have human societies completed their evolution in advance of any higher level of existence.
 That said, I do understand why Volk regards these societies as a base from which a new transformation may be occurring. I think it's actually somewhat arbitrary exactly where one places this transition point, but if one wants to single out these societies, then it seems to me one would also identify as a base level the human braina highly complex society of neuronsand before that, the genome in cells, a highly complex society of molecules. I will say more later about analogies between these levels which may help illuminate why I link these three forms of existence.
 The one exception I'm aware of is Pettersson (1996), who was the first to point out, to my knowledge, that stages of molecules existed within cells, and stages of multicellular societies existed within organisms that had critically different properties from cells and organisms themselves. This book received very little attention, however, and as far as I know, the author did not write any further on this subject.
 I have glossed over many important details. While bonding of small molecules into a biological polymer is potentially the source of a new dimension, how full and well-developed this dimension will be depends on the number of both the individual molecules, and of their interactions with one another. The completeness of the dimension also depends on to what extent the properties of the polymer are uncorrelated with those of the small molecule. There will always be some correlation, because the higher stage includes the lower; thus in the example discussed here, amino acid molecules include atoms, so there has to be some correlation. In fact, that there is some correlation is one way in which I define or identify a stage, and distinguish it from a level. A holon on one level is completely independent of an single holon on the level below it. Thus a cell is independent of any one of its component molecules, and an organism completely independent of any of its component cells. In contrast, a biological polymer is independent of some, but not all, of its individual atoms.
 When amino acids join into a peptide, they lose this property, because the ionizable groups responsible for bufferingthe amino nitrogen group and the acidic carboxyl groupform the peptide bonds that hold the amino acids together. This is another way in which I distinguish stages from levels. A new level, such as the cell, contains free amino acids, which retain all their properties. It also contains free peptides, free proteins, etc. In other words, a cell contains all the different stages, independently of each other. In contrast, any intermediate stage contains lower stages in a form in which they no longer exist independently.
 Conventionally, of course, it's understood that the genome carries all the information needed to reproduce the organism. But much of the organism's developmenteven early development, prior to emergence of movement, emotion and in our case, thoughtis controlled by programs in the central nervous system, which regulate activity of all the other major organs. We could say the brain picks up where the genome leaves off, and this is not so different from the genome's role in reproducing the cell, much of which has already been accomplished through mitosis.
 Notice, though, that the less involvement we have in these interactions, the greater the extent that our private experience can be shared. We all share to a large degree our experience of, for example, social rules and mores, because these are the result of interactions among very large numbers of individuals, past as well as present, and our own contribution to them is relatively slight. In contrast, we hardly share at all our personal thoughts or feelings about another individual, where interactions involving ourselves are dominant.
 Recent experiments suggest that the human visual system can actually detect single photons (Tinsley et al 2016). However, this conclusion only emerged after subjects underwent a very large number of trials, and were shown to report the presence of a photon at a level very slightly above chance. Single photons, or even several photons, are not experienced in anything the way that normal levels of light are.
Achard S, Salvador, R, Whitcher, B, Suckling, J, Bullmore, E (2006) A resilient, low-frequency, small-world human brain functional network with highly connected association cortical hubs. J Neurosci 26: 63-72.
Barabasi AL. (2002) Linked. New York: Perseus.
Barabasi AL, Bonabeau, E (2003) Scale-free Networks. Sci Amer 288: 60-69.
Bilke S, Peterson, C (2001) Topological properties of citation and metabolic networks. Phys Rev E Stat Nonlin Soft Matter Phys 64 (3 Pt 2): 036106.
Chalmers D. (1996) The Conscious Mind. Oxford: Oxford University Press.
Chalmers D (2000). What is a neural correlate of consciousness?, in Neural Correlates of Consciousness: Empirical and Conceptual Questions. T. Metzinger, Eds. Cambridge, MA: MIT Press. pp. 18-39.
Davidsen J, Ebel, H, Bornholdt, S (2002) Emergence of a small world from local interactions: modeling acquaintance networks. Phys Rev E Stat Nonlin Soft Matter Phys 88: 128701.
Ebel H, Mielsch, LI, Bornholdt, S (2002) Scale-free topology of e-mail networks. Phys Rev E Stat Nonlin Soft Matter Phys 66 (3 Pt 2A): 035103.
Hilgetag CC, Burns, GAPC, O'Neill, MAO, Scannell, JW, Young, MP (2000) Anatomical connectivity defines the organization of clusters of cortical areas in the macaque monkey and the cat. Philos Trans R Soc Lond B Biol Sci 355: 91-110.
Jablonka E, Lamb, MJ (2005) Evolution in Four Dimensions. Cambridge, MA: MIT Press.
Jeong H, Tombor, B, Albert, R, Oltvai, ZN, Barabasi, AL (2000) The large-scale organization of metabolic networks. Nature 407: 651-654.
Malenka RC (2002). Synaptic Plasticity. In Neuropsychopharmacology: The Fifth Generation of Progress. K. L. Davis, D. Charney, J. T. Coyle and C. Nemeroff, eds. New York: Williams and Wilkins, pp. 147-157.
Merzenich MM, Kaas, JH, Wall, J, Nelson, RJ, Sur, M, Felleman, D (1983) Topographic reorganization of somatosensory cortical areas 3b and 1 in adult monkeys following restricted deafferentation. Neuroscience 8: 33-55.
Merezenich MM, Nelson, RJ, Stryker, MP, Cynader, MS, Schoppmann, A, Zook, JM (1984) Somatosensory cortical map changes following digit amputation in adult monkeys. J Comp Neurol 224: 591-605.
Pettersson M (1996) Complexity and Evolution. Cambridge: Cambridge University Press.
Serio TR, Lindquist, SL (2000) Protein-only inheritance in yeast: something to get [PSI+]-ched about. Trends Cell Biol 10: 98-105.
Smith, AP (2002) God is not in the quad. A summary of my challenge to Wilber.
Smith, AP (2006a) Holarchic sense and holarchic nonsense.
Smith, AP (2006b) Holons within, holons without. Uniting developmental and conceptual relationships.
Smith, AP (2008) The Dimensions of Experience. Xlibris
Sporns O, Zwi, JD (2004) The small world of the cerebral cortex. Neuroinformatics 2: 145-162.
Tinsley, JN, Molodtsov, MI, Prevedel, R, Wartmann, D, Espigule-Pons, J, Lauwers, M, Vaziri, A (2016) Direct detection of a single photon by humans. Nature Comms 7: 12172
Visser, F (2018) Looking for the grand sequence. An integrally-informed review of Tyler Volk's Quarks to Culture, www.integralworld.net
Wuchty S (2001) Scale-free behavior in protein domain networks. Mol. Biol. Evol. 18: 1694-1702.
Yook SH, Jeong, H, Barabasi, AL (2002) Modeling the Internet's large-scale topology. Proc Nat Acad Sci USA 99: 13382-113386.
Yook SH, Oltvai, ZN, Barabasi, AL (2004) Functional and topological characteristics of protein interaction networks. Proteonomics 4: 928-942.