"Symmetry--an important feature in biological organization--is the outcome of repetition. The term is usually confined to spatial repetition. But we can also have repetition in time and this is called rhythm. Biological organization involves both."

"Whenever anything lives, there is, open somewhere, a register in which time is being inscribed."

Until the beginning of this century, the lowest form of existence was thought to be the atom. The atomic theory of matter was formulated by John Dalton in the early 19th century, but the existence of atoms had been postulated by the Greek Democritus several thousand years earlier. Traditionally, then, atoms represent the lowest level of the hierarchy, and they make a convenient starting point for our discussion. In a famous poem glorifying the Great Chain of Being, Alexander Pope referred to its downward reach through angels, human beings, and animals, to "what no eye can see, no glass can reach."3

Scientists do recognize today, of course, that atoms are not indivisible, but are composed of still smaller forms of existence: electrons, protons, neutrons, which in turn are made up of quarks, leptons and gluons. Despite the extraordinary and now well-publicized discoveries that constitute the new physics, however, I believe that what we know about these subatomic phenomena has not really added significantly to our understanding of hierarchical principles. The beginnings of holarchy may perhaps be seen in the ordered combinations of quarks and leptons in the atoms, and particularly in three families of these particles that seem to differ in size but not in their properties (Feynman 1988; Lima-de-Faria 1988; Glashow 1991). Nevertheless, existence at this level appears to be so rudimentary that we can barely perceive the principles that are so evident at higher levels.

Or it may be that this level is so distant from our own that we can't see it very clearly. An important principle of the holarchy, which will emerge in our later discussion, is that our perception of phenomena depends on where in the holarchy they exist in relation to ourselves. Because subatomic processes are several levels below our own, on a scale of both time and space very different from the ones we are most familiar with, it may be difficult for us to see these processes in the same way that we see those on higher levels. Certainly there are some very strange observations emerging from quantum physics (Capra 1975; Herbert 1985; Feynman 1988; Glashow 1991; Weinberg 1992; Horgan 1992; Seager 1999), the very existence of which suggests to some theorists that our understanding of it is fundamentally flawed or incomplete (Penrose 1989, 1994). In a later chapter, I will be discussing some of these quantum phenomena in connection with our understanding of human consciousness.

For now, however, I will pay them no heed, and begin this account of the holarchy with atoms. We can say that the physical level of existence begins with them, while recognizing that this level is not really the lowest level of existence. Indeed, a few scientists, like physicist John Barrow, question whether it is even meaningful to talk about a lowest level at all:

Whether or not Barrow is correct, his words underscore the point that our understanding of lower levels is likely to flawed in certain respects, with the result that we may not be able to see and know these lower levels in the same way we can see and know higher levels. More of this later.

Atoms have traditionally been considered lifeless forms of matter. They don't seem to have any of the properties that we normally associate with living things, such as growth, reproduction, or even death. Yet closer scrutinty reveals that atoms do have several important features that seem to presage those of living things. Indeed, we can see in atoms, albeit in an exceedingly primitive form, three major properties that we usually associate only with life: growth or assimilation; self-maintenance or adaptation; and communication.

Assimilation is exhibited by atoms when they gain an electron, a process called ionization. As writer and entrepreneur George Land pointed out in an insightful early formulation of the modern holarchical view, the atom can be said to grow in the simple sense that it incorporates another substance or form of energy, and becomes larger (Land 1973). This growth, however, is severely limited, in that any individual atom can generally gain only one or at most a very small number of electrons (which are almost vanishingly small in size compared to the atom), at which point the process can go no further.

The process of ionization can also be viewed, in some circumstances, as an example of adaptation, or self-maintenance. Higher forms of life, as is well known, must be able to adapt to changed conditions in order to survive. For example, if the environment surrounding an organism becomes much colder, the organism's body responds in certain ways--such as shivering, or increasing its rate of metabolism--to compensate for the decreased temperature. Ionization of an atom performs, on a simpler level, the same basic function. Thus when metallic sodium is placed into water, it ionizes, in this case losing rather than gaining an electron and becoming positively charged. By ionizing, the sodium becomes more stable in the new environment in which it finds itself.

Finally, atoms can communicate, by forming chemical bonds with other atoms. In this process, two atoms exchange or share one or more of their electrons. Communication at higher levels of existence is traditionally defined as a transmission of information, and chemical bonding of atoms might be considered to fall within this general definition. That is, we could say that in the process of sharing electrons, atoms are transmitting information to each other. Indeed, I will argue later that information simply is communication, of atoms or of analogous holons on higher levels of existence. For now, though, we can simply define communication as a hetarchical interaction, that is, one occurring between two holons on the same level of existence.

In summary, atoms display three fundamental properties that are found in all higher forms of existence, and which are usually taken as features of living things. I will argue later that by adding just one further property to this list--reproduction--we can account for all known phenomena of all holons. That is to say, all the complex and sophisticated behavior of even highly-evolved creatures like ourselves can be classified as one of these four fundamental properties.

The systems theorists Francisco Varela and Humberto Maturana want to go even further than this (Varela et al. 1991; Maturana and Varela 1992; Varela 1994). In their theory of autopoiesis, living things, at least at some levels, are defined essentially through adaptation, or self-maintenance: "an autopoietic machine continuously generates and specifies its own organization through its operation as a system of production of its own components."5 This definition allows autopoietic theory to dispense with direct references to growth, reproduction, or even evolution (Luisi 1993).

Varela and Maturana, in other words, are groping for a unified definition of life that incorporates all kinds of properties in it. I believe that such a definition may be possible, and is certainly a worthy aim of holarchical theory. However, the definition quoted above clearly does not apply to atoms, nor to many other types of holons I will be discussing in this chapter. So I will stick with the properties that I have enumerated here, though we will see shortly that there is in fact a way in which they can be understood as different aspects of a single property.

If most of the fundamental features of life can be observed, even in very primitive form, in atoms, we might argue that as higher forms of life emerge, there are no truly "new" properties, but simply more complex and sophisticated ways of expressing the basic, fundamental properties. Thus philosopher Michael Polanyi suggested that evolution is simply "a progressive intensification of the higher principles of life"6 which are already present from the very beginning. Lima-de-Faria, a biochemist, devotes an entire book to this idea, summarized here:

This view is not an attempt to reduce the higher to the lower, but rather to show that it's constrained by the lower. More precisely yet, the higher is constrained by principles that don't necessarily originate in the lower, but are first evident (to us) there. In contrast to the extreme Darwinian view, which with little caricature might be presented as "anything is possible, everything is unlikely", Lima-de-Faria and others argue that some evolutionary paths were much more likely than others, perhaps even inevitable. "Natural selection does not always determine the evolution of morphology," argues Stephen Jay Gould; "often it only pushes organisms down a preset, determined path."8 I will be discussing this issue in detail in Part 2 of this book, when we consider the processes of evolution. Here I only want to emphasize that these arguments have their beginnings at the physical level. To the extent that we can see in atoms some of the same processes that we see in cells and in organisms, we must begin to wonder if the choices evolution made might have been neither random nor unlikely.

I said a moment ago that there is an even simpler way to define the three properties of atoms that we have examined so far. Each of these properties--assimilation, adaptation and communication--can be defined in terms of the kind of holons with which the holon exhibiting the property interacts. That is to say, assimilation can be defined as the process by which a higher-order holon (atom) interacts with a lower-order holon (electron). Adaptation is the process by which a lower-order holon (atom) interacts with a higher-order holon (molecule). Communication is the process by which two holons of the same kind interact. Thus every property of a holon is embodied in its interaction with some other holon. This statement, for now, excludes reproduction, which will be discussed in Chapter 3.

An important corollary that emerges from defining these properties in this manner is what might be called the law of perspective: Every holon or process of interaction of holons can be viewed from multiple positions in the holarchy; a process appears different according to the relative position from which it's viewed.

Consider again the last example presented above--that of two atoms forming a chemical bond with each other. What, exactly, has happened? I said a moment ago that this was an example of communication, and so it is--from the point of view of the atoms themselves. From the point of view of the electrons which are shared during this process, however, the process is adaptation--they have changed the way they interact with the larger holon, the atom, with which they are associated. In fact, each of the shared electrons is now interacting with not one atom but with two.

Further suppose that one of the two interacting atoms is part of a larger holon, a molecule. When this atom forms a bond with another atom, the latter becomes joined to the molecule. From the molecule's point of view, then, the process is assimilation; it has incorporated another atom, and grown larger.

Communication, assimilation, adaptation--it all depends on who you are, which is to say, where you are. This example, as we will see, can be multiplied endlessly, at all stages and levels of existence. While many properties of life appear at every level of existence, the nature of the property depends on the point of view of the holon, which in turn depends on its holarchical relationship to the phenomenon. What the property 'really' is can never be pinned down; it has a different identity on every plane of existence. It is in this important sense that we can say that there is only one fundamental phenomenon occurring, but many ways to see it.

As we will see later (Chapter 4), the law of perspective may become very important when we try to assess the degree of analogy between a holon on one level of existence and one on another--particularly our own level. As holons ourselves, we have a characteristic way of looking at both ourselves and other holons. The law of perspective also will prove to have a vital bearing on our understanding of mind, and its relation to the physical and biological world.

The example of two atoms bonding together to form a molecule is of particular relevance to understanding the holarchy, because all higher forms of existence, it should be apparent, involve molecules, or organizations of molecules. In a moment, we will examine some of these higher forms of existence. But first, I want to point out that some atoms are much more interactive--or as chemists would say, reactive--than others. In fact, chemists make a distinction between reactive atoms, those which can form chemical bonds with other atoms; and inert atoms, which don't form such bonds. Hydrogen and oxygen are examples of reactive atoms, while helium is an example of an inert atom. Reactive atoms have electrons that they can share with other atoms in chemical bonds, while inert atoms have no such shareable electrons.

Clearly, only reactive atoms can create higher forms of life. There is no helium, or other inert elements, present in cells and organisms. Furthermore, of all the reactive atoms, there is one in particular that is the basis or "building block" in traditional language, of life. This is carbon. Carbon, unlike most other atoms, can form chemical bonds with four other atoms simultaneously. This property allows it to create complex chemical compounds which make up all cells and organisms. Thus carbon, because it is highly interactive or communicative, is the keystone to the higher stages of physical existence.

When two or more atoms join to form a molecule, something new appears. A molecule has properties that are not possessed by its component atoms. A simple example is provided by water, which consists of two hydrogen atoms and one oxygen atom. Water, of course, is very different from either oxygen or hydrogen. The latter are gasses at room temperature, highly compressible and of very low density. Water is a liquid under the same physical conditions, almost completely incompressible and of much higher density.

A much better example of emergence is offered by a somewhat more complex molecule, an amino acid (Fig. 1). Amino acids are found in all living things, where they exist both as free molecules and as parts of proteins. There are about twenty different kinds of amino acids commonly found in cells and organisms, but all of them have the same basic structure. They consist of several carbon atoms, terminating at one end with nitrogen (the amino group), and at the other end in carboxylic acid (the acid group).

A characteristic feature of all amino acids is the ability to ionize in two positions--on the amino end and on the carboxyl end. This seemingly simple property is highly significant, for it allows amino acids to act as buffers, that is, to stabilize the pH, or degree of acidity, within the cell. If the pH becomes too low (too much acid), hydrogen ions are added to the amino and carboxyl groups; it the pH becomes too high (too much base), these hydrogen ions dissociate from these groups (Fig. 1).

As we saw earlier, some atoms, such as sodium, can also ionize. However, this process is for all practical purposes irreversible. If sodium is added to water, all of the atoms ionize. In contrast, the degree of ionization of an amino acid can be changed over a continuum. This is possible because the presence of other atoms in the amino acid stabilizes the ionized atoms. Through a process of sharing electrons, these adjacent atoms allow the nitrogen of the amino group or the oxygen of the acid group to remain in a charged or uncharged state under a variety of conditions. This is a genuinely emergent property found only in molecules.

To summarize, if atoms are considered the lowest type of holon on the physical level, the next-higher order holon is represented by certain fairly simple molecules such as amino acids. Such molecules are composed of atoms, yet have properties not possessed by their component atoms, or indeed, by any atoms. These properties are emergent with the appearance of molecules.

The holarchy present within cells doesn't end here, however. Polymers like peptides and nucleic acids can, in turn, combine to form still higher-order holons, which are generally referred to by cell biologists as simply supramolecular structures. These, in turn, may be part of still larger holons, subcellular organelles. Each of these holons has emergent properties, which I will discuss as we go along. I have listed them all in Table 2 ; taken together, they compose the physical level of existence, beginning with atoms and ending in cells.

The exact arrangement of these holons is somewhat arbitrary, but the general principle of holarchical arrangement within cells is very well established. Thus cell biologists Becker and Deamer remark that "biological structures [i.e., those within a cell] are almost always constructed in a hierarchical manner...This hierarchical process has the advantage of chemical simplicity and efficiency of assembly."9 We will see examples of such advantages, and others, as we go along. And in Chapter 3, I will discuss at some length just why and how holarchical organization is used by living things.

There is one aspect of the hierarchical arrangement in Table 2 that is not arbitary, however. This is the marking off the beginning of the physical level with atoms, and the end with cells. As I noted in the beginning of this chapter, there are holons below the atom, and as we will see, there are holons above the cell. Both atoms and cells, however, have a special quality or property that distinguishes them from any of the holons immediately below or above them, or from those between them. Both are capable of an independent (autonomous) existence outside of higher forms of life. While some atoms exist as components of molecules, they may also be found as free forms of matter not bonded to each other. Likewise, cells can exist as unicellular organisms as well as components of organisms. This distinction is also noted by Petersson10.

In contrast, virtually all holons between atoms and cells exist solely within cells. Molecules, with the exception of very simple ones containing one or two types of atoms, are generally not found free in nature. (And as we saw earlier with the example of water, the emergent properties of such molecules are very slight.) Even more so is the case for simple and complex polymers, macromolecular structures, and sub-cellular organelles. While many of these subcellular components can be isolated and studied in the laboratory, in nature they almost always exist only within cells.

Thus on the basis of what we find within cells, we can define at least two kinds of holons: those that can exist more or less independently of higher-order holons and those that can't. I will call the first type of holons, exemplified by atoms and cells, as fundamental or autonomous holons, and the second type, exemplified by various kinds of molecules found within cells, as intermediate or social holons. I further propose that we define the entire set of holons ranging from atoms to cells as a single level of existence, while referring to any particular type of holon within that level (such as an amino acid or a protein molecule) as a stage within that level. (To encompass either term, I suggest the use of "plane" of existence, though because of its widespread usage, I will sometimes use "level" in this sense.) Thus atoms are the first stage on the physical level of existence, while cells, as we will see in the next chapter, are the first stage on the biological level of existence.

In addition to being capable of autonomous existence, cells and atoms are organized somewhat differently from the way other types of holons are organized. To appreciate this, consider first the higher-order, intermediate stages within cells: small molecules, polymers, and so on. Each of these holons consists of a large number of holons of the next-lower stage, all combined into one entity. Thus small molecules consist of atoms, all joined to one another; polymers consist of small molecules, all joined together; higher-order molecular structures consist of associations of polymers.

In contrast, in a cell, all of the lower holons can exist both semi-autonomously (i.e., not components of the next higher stage) as well as in bonded (joined) forms (in which they are components of the next higher stage). Thus some atoms exist semi-autonomously in cells (e.g., sodium and calcium ions), while others exist as components of small molecules. Some small molecules, in turn, exist semi-autonomously (individual amino acids), and some as components of polymers. Some polymers exist free, while others are components of higher-order structures.

A cell, in other words, not only has new, emergent properties not found in its lower, component holons, but also preserves the properties of the lower holons. For example, the properties of amino acids are preserved within a cell, because some of these amino acids exist in a semi-autonomous form in which they behave more or less as though they were completely isolated, i.e., in a test tube. Likewise, the properties of certain atoms, such as sodium, are preserved within cells, because these atoms can exist in a semi-autonomous state much like that of these same atoms outside of cells. Petersson refers to this as the "duality criterion":

In contrast, the properties of amino acids are not preserved in a peptide or protein. The ability to ionize, for example, is lost, because when amino acids combine with one another to form peptides or proteins, both the amino and carboxyl ends of the molecule are joined to neighboring amino acids. These ends are no longer free to ionize. Likewise, the properties of individual atoms are not preserved when they are combined into molecules, because many of their properties depend on the present of electrons which become shared with other atoms within the molecule.

I will not discuss the internal organization of the atom in this context, though it appears to be analogous to the cell in this respect. Later, however, we will see that a similar type of organization is present in organisms, which constitute a fundamental stage on a still higher level of existence.

An essential principle of the holarchy, as we saw earlier, is that new, emergent properties appear with higher levels or stages of existence. Thus a molecule has properties not found in its individual atoms; a peptide has properties not found in its component amino acids; a cell has properties not found in any of its component holons.

Why, or how, do these new properties emerge? Emergence is sometimes regarded as unexplainable, a "gap" in the holarchy, since the new properties of the higher holon do not reduce to those of its lower-order component holons. In many cases, however, the mystery is overstated. Scientists do understand fairly well how the properties of higher-order molecules in the cell emerge, and can explain them to a large extent in terms of physical principles. A closer look at these principles in fact allows us to provide a new, and more powerful, definition of a stage. A stage is a new dimension of existence. Literally.

Consider again the level formed between atoms and cells. An atom can be taken, from a certain perspective, as a point, having no dimensions. This is only relatively true, of course. An atom has actual dimensions that can be measured. But for purposes of comparison with other forms of existence, we can regard atoms as so small that they exist as zero-dimensional points.

From this perspective, a simple molecule such as an amino acid can then be viewed as a linear array of atoms, or a one-dimensional form of existence. A simple polymer such as a peptide may also exist as a one-dimensional structure; in fact, the amino acid sequence of a peptide is known as its primary structure. More often, however such polymers fold into a planar or secondary structure, such as an ?-helix or a ?-sheet, which we can regard as a 2-dimensional form of existence. Still other polymers, such as globular proteins, feature folding of secondary structure into tertiary structure, which has three dimensions (Fig. 2; Stryer 1988).

Still higher physical stages can be understood in terms of further physical dimensions. Thus biochemists speak of quaternary structure, formed by the folding of a three-dimensional structure. Furthermore, the association of many molecules with quaternary structure into a higher-order holon could be considered, in some fashion, as still another physical dimension.

However, higher dimensions may also be understood in terms of time. A macromolecular structure such as a receptor molecule has three spatial dimensions, but to understand its function, and thus its very existence, these dimensions must be viewed in time. This is because such biomolecules change shape or conformation in certain characteristic ways as they function in the cell.

Consider, for example, an ion channel, which is a pore in the cell surface membrane formed by one or several protein molecules (Fig. 3). Certain ions pass in or out of the cell by going through this pore, and their flow is regulated by changing the size and or shape of the pore. The latter, in turn, results from a change in shape (what biochemists call conformation) of the proteins forming the pore. Whenever an ion channel is activated--by certain neurotransmitters, for example, or by a change in the voltage across the membrane--these proteins change their shape, open the pore, then after a certain period of time, revert to their original shape, closing the pore (Smith 1989; Aidley 1996).

Thus the ion channel, as a meaningful functional unit, has a temporal dimension as well as spatial ones. The effective existence of the channel is not as a fixed three-dimensional structure, but a three-dimensional shape that changes over a period of time. Taking this period of time as the window, so to speak, in which we examine it, its existence emerges as four-dimensional, relative to the zero dimensions at which we have abitrarily fixed the atom.

We can view an active enzyme molecule in the same manner. When an enzyme catalyzes a chemical reaction, it begins by binding to a certain substance, called its substrate. To do this, the enzyme must change its shape or conformation, so that the substrate fits into a certain portion of the enzyme's surface (Stryer 1988). The substrate is then converted into another type of molecule, the product, which is then released from its interaction with the enzyme; as this occurs, the enzyme's shape changes again, reverting to its original conformation. So an enzyme molecule, like an ion channel, is four-dimensional when active, repeatedly cycling between two different shapes or conformations. A single enzyme molecule may undergo hundreds of such catalytic cycles in a second.

A second dimension of time appears in still higher-order macromolecular structures, or in subcellular organelles. These structures consist of many four-dimensional holons--that is, three-dimensional molecules cycling through a fixed period of time--which, as a unit, are moving through a second period of time. This second period of time adds a fifth dimension to the holon.

For example, all cells have a surface membrane that completely surrounds them, and which acts as a semi-permeable barrier between them and the surrounding environment. This membrane has a very large number of ion channels, which allow the cell to take in, or pass out, different kinds of ions. When this happens, each of the many channels may open and close a great many times. Thus the event of membrane permeability is composed of a great many cyclical events. The unit time of the ion channel is repeated to form the unit time of the cell membrane (Fig. 4).

In summary, higher order physical stages can be defined in terms of the number of new dimensions they bring into existence. To be sure, these dimensions are not mathematically precise; genuine dimensions in the mathematical sense have a relationship of infinity to each other. Thus a one-dimensional figure such as a line contains an infinite number of points, and a two-dimensonal plane contains an infinite number of lines. The relationships between the spatial and temporal dimensions I have discussed here are not infinite. Neither, however, are these relationships characterized by simply greater extension in the same dimension.

The key to understanding this lies in the concept of repetition. A point that simply becomes larger can still be considered a point; a point that repeats itself becomes a line. A line that simply becomes longer is still a line; a line that is repeated as other lines becomes a plane. Holarchy is comprised of repetitive units. A molecule contains many atoms; a protein contains many amino acids; an active enzyme is composed of many catalytic cycles. In this important sense, a molecule is one-dimensional relative to an atom, and a protein is two or three-dimensional relative to an atom. A protein that changes shape in a cyclical fashion is repeating itself in time. A set of proteins that do this is repeating itself in a second dimension of time.

I will have much more to say about dimensions of space and time as we go along, for as we shall see, similar relationships exist on higher levels. Defining dimensions in this way, I believe, not only helps us understand how new properties come into existence, but how, and to what extent, these properties are already present, in primitive or rudimentary form, from the beginning. I suggested earlier that three of the basic features of existence--assimilation, adaptation and communication--are found in atoms. In some sense, atoms, too, exist in higher dimensions. They do have extension in three dimensions of space, and since they can move in this space, we can talk about dimensions in time as well. But these higher dimensions of atoms are much less-developed than they are in the higher physical stages of existence. So we could say either that new dimensions of space and time come into existence with higher forms of life, or that these dimensions simply develop, or unfold, in the higher stages of they physical level. We will see the same situation at higher levels of existence.

In all cases, the new dimension of existence that emerges with each successively higher stage is directly related to that stage's emergent properties. The emergent properties become possible precisely because of the existence of the new dimension available for the holon to function on. For example, as we saw earlier, one of the most important emergent properties of small molecules is the ability to ionize. One of their component atoms can lose or gain an electron, resulting in an electrical charge associated with the molecule. This charge is stabilized by the presence of other atoms bonded to the ionized atom--the linear dimension of the molecule--and for this reason, reversible ionization of an atom generally occurs only within molecules.

Likewise, higher dimensional holons on the physical level have properties that depend on their higher degree of dimensionality. For example, the three-dimensional or four-dimensional quality of proteins is critical to their ability to act as enzymes, to catalyze metabolic reactions and perform other vital functions in the cell. The three-dimensional shape enables the protein to interact with other molecules in highly specific ways, forming a precise fit between their surfaces. Again, this property could not emerge without these critical extra dimensions. The four-dimensional property, as we saw, enables the enzyme to undergo catalytic cycles.

In addition to these rather specific emergent properties of higher physical stages, there are some more general ones that follow directly from existence in a higher number of dimensions. One of the most fundamental of these properties, which we will encounter again and again as we examine other portions of the holarchy, is that higher-order holons have a longer lifetime than lower-order holons. All holons in the cell, except atoms, are constantly turning over, that is, being degraded and replaced by equivalent new holons. Thus they have a finite lifetime. Molecules such as amino acids have a very transient existence in the cell; if they are not incorporated into peptides or proteins, they are quickly metabolized. Peptides and proteins have a longer lifetime, measurable in hours or days, or sometimes several weeks (Creighton 1993). Cells may live for weeks or months12. Organisms live longer than cells. Processes within each type of holon also occur on different scales of time (Haldane 1956).

A second fundamental property, closely related to the first, is that higher-order holons have more stability than lower-order holons (Simon 1972). There are several ways of understanding stability, but for now I will simply define it as the degree to which a higher-order holon is independent of its lower-order holons. Because the higher physical holons are composed of many lower holons, they usually are not dependent on any one of the latter for their existence, or for any of their main properties. For example, we could remove a single atom from an amino acid, or replace it with another atom (to the extent that physical laws permit such replacement), and the amino acid would probably still be able to ionize (a form of adaptation), as well as to form chemical bonds with other amino acids (communicate). This is readily seen in that there are about twenty different amino acids found in nature, each differing slightly in their atomic composition, but each of which possesses the ability to ionize and to link up with other amino acids (Stryer 1988).

In the same manner, we could remove or replace any single amino acid from a large peptide or protein molecule, and in most cases, this will not alter the protein's properties. If the protein is an enzyme, it will retain its enzymatic activity. If protein is part of a receptor, interacting specifically with some ligand, it will retain its ability to do this. Again, the proof of this is found in the presence of closely related families of proteins, such as enzymes and receptors, members of which differ in some of their amino acids, yet which nonetheless have the same properties (Creighton 1993; Gerstein and Levitt 1997; Patthy 1999).

I believe stability is a particularly important emergent property, because it helps greatly in classifying different stages of existence within any level of the holarchy. As I noted earlier, these stages appear at first glance to be somewhat arbitrary. In the cell there are many different kinds of molecules, of all sizes and compositions, and if we defined each stage as simply any molecule that contained other molecules, or atoms, we would have a virtually infinite number of stages. But when we apply the criterion of stability, many of these holons are seen not to constitute genuine stages. This is why I don't regard simple molecules such as water and carbon dioxide, for example, as higher stages. Change or remove any one atom of such molecules, and the properties of the molecule are drastically altered. Likewise, there are many holons in the cell formed of a few larger molecules, but which are not highly stable by the definition used here. Such stability, it should be apparent, depends on the higher-order holon containing a fairly large number of lower-order holons.

We will see later that these same relationships hold as we move to higher levels of existence. Thus tissues and organs within organisms live longer, and are more stable, than their individual cells; likewise, organisms live longer, and are more stable, than their component tissues and organs. Furthermore, many other emergent properties result directly from the fact that higher-order holons function on a larger number of dimensions of both space and time than do lower-order holons.

Another way to express this point, as argued by the mathematician and mystic P.D. Ouspensky, is to say that higher dimensions can be understood in terms of the actualization of possibilities (Ouspensky 1961, 1971). Though his argument was directed towards dimensions of time, I think it also applies to space, and is somewhat easier to understand in this manner. Consider an atom in the cell. If it exists autonomously, outside of higher holons, it functions in only one dimension. Yet it has the possibility of functioning in higher dimensions,by participating in higher-order holons. For example, if the molecule becomes part of a three-dimensional protein molecule, it may function in three dimensions. If the protein has a function in time, the molecule may function in four dimensions. But since the limit of such participation is reached at the next level--that is, an atom reaches its limit at the cell--we can say that a cell represents the actualization of all possibilites of the atom. Everything that is possible for an atom is realized in the cell.

One of the most powerful features of understanding holons in terms of dimensions of time as well as space is that it enables us to see the relationship between what is commonly called a structure, and what is called a process. One of the commonest criticisms of traditional science by those interested in creating a new worldview is that science reduces everything to structures--atoms, molecules, cells, organisms, and so forth--and is not concerned enough with processes. Of course scientists are very much aware of processes, but they tend to give them second billing, defining them as the movements of various structures. For example, metabolic processes in cells are described in terms of reactions in which specific kinds of molecules are transformed into other kinds of molecules. A process, so defined, seems to be reduced to something that a structure does. The structure is primary.

In contrast, many critics of traditional science seek to replace this understanding with one in which process, rather than structure, is emphasized (Capra 1996). In this view, everything is in constant flux, and what we call structures are simply snapshot views taken at particular points in this flux. Since no point in the flux is really any more important than any other, they argue--or at the very least, no point is permanent--focussing on these snapshots distorts the picture. The reality is the flux, the process.

Understanding that holons can have dimensions in time as well as space, however, helps us adopt a view in which both structure and process have a place. Time is obviously a central feature of any phenomenon that we call a process. To say that something is a process implies that there is movement or change in time. In the holarchical view, however, our awareness of time depends on our relationship in the holarchy to the phenomenon of interest. Hold up your hand and look at it. Would you call it a structure or a process? Most people would call it a structure. The hand is also a process, however, in fact, a set of a great many processes--it contains millions of cells and perhaps billions of molecules, and these cells and molecules are rapidly changing. But we are ordinarily not aware of these processes. Why?

We are not aware of these processes because we are so far above the levels of cells and molecules in the holarchy that we can't perceive the dimension of time in which these processes occur. This dimension of time is not irrelevant to us. It is actually incorporated, along with the dimensions of space, into the properties of cells and molecules that manifest themselves to us as a hand. But because we can't see this dimension of time, because we have completely transcended it, we call the hand a structure.

Now consider what happens when we watch other people, working, playing or engaging in other activities. What do we see? I think most people would say they have some awareness of both structure and process. We see other people as separate, identifiable organisms, that is, as structures. But we also have some awareness that they are moving and changing in time, have relationships to other people, and so are part of a process. Unlike the case with our hand, we have not transcended the level on which other people live; it is in fact our level. Since the stages on this level in which we exist have dimensions of time as well as space, we have some awareness of this time, and perceive events to some extent as processes.

Finally, consider the thoughts moving through your mind. Are these thoughts structures or processes? Most people would call them processes. Yet in the holarchical view, they also involve interactions of holons, just as a body part like the hand does, or people in various activities do. Why, then, do we perceive our thoughts as processes? I will argue later that we see them that way because the holons involved are not below us, like cells and molecules, nor on our level, like other people, but actually above us, in the form of the human social organizations we belong to. Thoughts are what we see when we look at these holons. And because they are above us, the main way in which they differ from us is that they exist in dimensions of time that are beyond those of individual organisms. By virtue of our participation in these higher dimensions, we can have some awareness of this time, and thus our view of them is as processes.

To summarize, as we move up the holarchy, we may see both structures and processes. When we transcend one level, these structures and processes are synthesized, in our perspective, in a new, higher-order structure which includes both time and space in its dimensions. This higher-order structure then may participate in new dimensions of time on the next level. Both time and space are always around us, but depending on where we are, and what we are looking at, we may be more aware of space, as when we see a structure, or more aware of time, when we see a process.The implications of this for ourselves and our relationships to others will be discussed further in Chapter 4.

One such concept, that I want to introduce now, is freedom. The word freedom obviously has many different meanings to us, which makes it very difficult to give it a precise definition. We talk about political freedom, religious freedom, economic freedom, artistic freedom, even scientific freedom. These different concepts may be related to each other, but clearly are not the same thing. A person may experience, or believe she experiences, some of these freedoms without necessarily believing she enjoys all of them.

This suggests that we may be able to use the concept of freedom to describe the position of any form of life in the holarchy. That is, we might say that the higher in the holarchy a holon is, the freer it is. A cell is freer than a molecule; a tissue freer than a cell; an organism freer than a tissue. In each case, the new degree of freedom can be appreciated in terms of the properties discussed in this chapter. The higher is freer than the lower in the sense that it exists in a greater number of dimensions; that it's more stable; that it has a longer lifetime; and that it's subject to fewer constraints.