For at least a hundred years, science has been one of the principal ways we imagine our relationship with nature; science has enormous prestige in our culture, whether or not it is well understood. We live in a strange mash-up of different eras, where Newtonian ideas of causality are taken for granted and at the same time, New Age spirituality talks about higher mind residing in the quantum field. My thinking has recently been influenced by a contemporary branch of science known as systems biology, because this discipline holds new insights that I believe have the power to change how we imagine what life is.
I hope, and I believe, that the various thinkers whose ideas appear here actually do justice to the workings of the world around us in their accounts of living systems. On the other hand, I can’t prove that they’re right. But my train of thought doesn’t ultimately rest on whether they can be proved objectively correct; what I’m trying to get at, in the end, is the possibility and the effects of imagining the natural world in certain ways.
Some readers might object that it makes no sense to base anything on ideas, scientific or otherwise, that can’t be proved objectively correct. I’d like to remind them that science doesn’t prove anything; it can only disprove. A scientific hypothesis, under the definition created by the philosopher of science Karl Popper, is one that predicts something which can be proved false. If it cannot be disproved – like, for example, astrology – then it isn’t part of the process of science. If experimental observations are consistent with a hypothesis (do not prove it false), if no one can poke a hole in the design of the experiment or the technique with which it was carried out, the work may get published. Other labs try to replicate the experiment, to see if they independently come up with the same findings. If they do, the original hypothesis becomes stronger, more trustworthy. Scientists operate through skepticism; they try to find other theories that could account for the same phenomena, to design experiments that will test theories in novel ways. The more a description of reality is tested and found consistent with what is actually observed, the more we rely on it to work in the future, until it gets to the point where what was once a hypothesis is universally accepted in the scientific community. But this does not mean that it has been proved objectively true. There always remains the possibility that a future observation could show that the hypothesis was incomplete, inaccurate in some respect, not universally applicable.
The proof that can happen is proof that a hypothesis is objectively untrue. If I propose as a law of nature that dogs always chase cats when they see them, then only one dog observed noticing, but not chasing a cat is enough to prove that I was wrong. But no matter how many cat-chasing dogs I observe, I will never have proved that it always happens.
So far as I know, there are no biologists who don’t believe that evolution occurs. Countless observations have confirmed that such a phenomenon has gone on as far back as the fossil record shows, and takes place all the time. Some evidence of evolution is well-known to non-scientists. Insects become resistant to pesticides all the time. Why? Because those the pesticide doesn’t kill are the ones who reproduce. We force the insect species to evolve in the direction of pesticide resistance, or else die off. Infectious organisms such as the tubercle bacillus, which causes tuberculosis, become drug-resistant by a similar process of forced selection, evolution driven by our intervention. We have to create a new flu vaccine every year because the flu virus constantly evolves through mutations and recombinations. Since Darwin, we have built up a colossal number of observations that tell us the concept of evolution is not false; yet all of the weight of this evidence doesn’t mean that evolution has been proved true. We do and we should act on the basis of enormous confidence in the mechanism of evolution, for example by trying to restrict the amount of antibiotics prescribed to people or fed to animals, because we know that heavy use of antibiotics will force disease-causing organisms to evolve in the direction of drug resistance that much sooner. But enormous confidence that this description of reality works on Earth, given everything we know so far, is not the same thing as saying that it is proved forever, universally, objectively true. A certain kind of humility comes with acknowledging that there is no such thing as being absolutely right, but there is such a thing as being demonstrably wrong.
This is the context I have in mind when I say that my thinking doesn’t ultimately rest on whether all the following ideas can be proved objectively true.
The four causes and complexity are at work in living systems
An ancient philosophical thought about causation is finding new applications in science today: Aristotle, in his Physics, asserted that there are four distinctly different kinds of causation at work in the world. They are known as material cause, efficient cause, formal cause, and final cause. Probably the quickest way to explain the four causes and the differences between them is to invoke the canonical example that philosophers use, which is to ask, What causes a house?
The material cause of a house is lumber, shingles, windowpanes, electrical wire, fixtures, water pipes, etc. – all the physical stuff it’s made out of.
The efficient cause of a house is carpenters, plumbers, electricians, roofers, etc. – the doers who take the stuff and make it into a building.
The formal cause of a house is the design, the pattern, the notion of its structure that becomes the architect’s plans.
The final cause of a house is that someone intended to have a place to live. Final cause is about purpose. The final cause is like the answer to the question “Why is there a house in the first place?” whereas the other causes are more like answers to “How is there a house?”
Or, as an alternative example, take the game of baseball.
Material cause: balls, bats, gloves, grass, dirt, bases, warning track, the rolled-up tarp in foul territory that a player might trip over, padding on the outfield wall, etc. – all the physical stuff players actually use.
Efficient cause: players, umpires, managers, coaches.
Formal cause: above all, the rules of the game. Also, the fact that it’s always 90 feet from home to first. The shape and size of the particular ballpark. Anything that is a parameter of relationship rather than a stuff to be used.
Final cause: Why is there baseball in the first place? Maybe because people love games.
In order to fully understand a house, or the game of baseball – at least according to Aristotle – you need to think about it in four ways that are different in kind. You could be the world’s greatest expert on obtaining building materials, but this alone would not lead to a complete grasp of what goes into building a house. You could know all the rules of baseball, but without specific players exerting their baseball skills there would be no game to understand. The causes are not only different, they operate independently of each other. Having a set of blueprints for a house doesn’t necessarily mean you know how to construct one; having carpentry skills doesn’t necessarily mean you possess the vision of an overall design. Having either one doesn’t automatically bring you the necessary building materials, and so on.
The independent, simultaneous operation of distinct kinds of causation is a direct link from Aristotle to the meaning of “complexity” as that word is used in systems biology. A complex system, like baseball, or – crucially – an organism or an ecosystem, is “complex” in a special sense of the word: you cannot fully represent the workings of a complex system by any one model. No one explanation accounts for all that goes on in it. Instead, you have to approach it from a number of different perspectives, make sense of its workings differently from each perspective, and remain aware that all your accounts of the system’s functioning are in operation simultaneously.
For example, an ecosystem is made up of organisms in complex webs of relationship through which they all thrive better together than they could on their own. These interdependent organisms can be as different as algae and striped bass; what they’re capable of doing with the nutrients the environment provides differs in fundamental ways. Plants are capable of photosynthesis, and they can metabolize inorganic compounds in ways animals cannot; when animals eat plants, they greatly speed up the transformation of plant matter into nutrients that can be used by further generations of plants (hence the use of manure as fertilizer). Even couching it in this simplified form shows that radically different explanations are required to account for all that’s going on in the ecosystem. Then imagine what happens conceptually when huge categories like “animals” and “plants” are replaced with dozens of different organisms, each with its own physiology and life cycle, all simultaneously having an effect on each other’s propensity to thrive. You begin to get a glimpse of what “complexity” means, and why it’s hard to get your mind around it.
On top of this, the ecosystem itself evolves; organic processes don’t acquire a structure and then maintain it forever. The environment is not changeless and neither are the ecosystems within it, even when we might like them to be. If life and life systems could not evolve, they would not be sustainable over the long term.
In an ecosystem it is not difficult to conceive of material and efficient causes. The material causes are the nutrients, or the solar energy, that the environment provides and that organisms can metabolize. The efficient causes – the doers – are the organisms themselves. But what makes it an ecosystem is the network of relationships among the organisms that make it up, in other words its structure – formal cause. The crucial point about an ecosystem’s structure is that it contains causal loops – not linear trains of causation, like those in a pinball machine, where no interaction can influence the ones that came before it. Instead an ecosystem’s functioning depends on feedback loops that circle back upon themselves. An ecosystem operates by, one might say, “circular reasoning.” The following diagram comes from Robert Ulanowicz, whose elegant and accessible book Ecology, the Ascendent Perspective has had a major influence on my thinking.
The boxes represent organisms, and the + signs on each arrow indicate increased activity. The functioning of organism A encourages the growth of organism B, whose activity supports an increase in C, and – closing the circle – C in turn accelerates the activity of A. What we see here is a system that constantly moves in the direction of increased activity through a positive feedback loop. This little circular system possesses “indirect mutualism.” A’s contribution to the growth of B is not returned in kind to A directly. There is no causal arrow from B back to A. Rather the chain of causes passes indirectly through C. But the effect remains mutual because an increase in the activity of any one participant in the cycle leads to an increase in the other two. The cycle is “autocatalytic” – self-enhancing.
Autocatalytic cycles – which is also to say, causal loops – are the reason why ecosystems can do what they know how to do so well: they allow every organism in the system to flourish better than it could on its own. In real life, of course, a mapping of the nutrient flows in an ecosystem is far more complex than this simple triad. Yet crucial points are made by this simple, idealized example.
This loop of causation has no starting point. The Aà B à C notation is misleading in that A comes first in the alphabet, so we are culturally disposed to think that A must be setting the process in motion. In reality, there is no prime mover. To identify any one organism as the initiator of the action is only a fiction; accurately seen, the process is simply ongoing.
In the autocatalytic cycle you see how the operation of formal cause is distinct from material and efficient causes. The circularity of the relationship, which allows ongoing positive feedback, is its crucial formal, structural property. It possesses this property completely independent of specific, identifiable nutrients (material cause) or specific, identifiable organisms (efficient cause). The formal property, the circularity, exists even in this abstract, symbolic rendering. It cannot be pointed to in any one localized part of the diagram; circularity is a property only of the whole diagram. Circularity does not in itself provide any nutrients or metabolize anything; but without this relationship among the organisms making up the cycle, there would not be self-enhancement.
So far, I’ve conveniently ignored final cause in talking about an ecosystem – conveniently, because final cause is the most controversial of the four causes in the context of science. For a long time, final cause has been ruled out of science because it involves purpose, intentionality; to put it another way, final cause involves the future acting upon the present. This is categorically an impossibility in a mechanistic Newtonian world where linear chains of material and efficient cause constitute a sufficient explanation of reality. I don’t want to say that an ecosystem is caused by a purpose, but it definitely has a direction: its interconnectedness, and the level of biological activity within it, both increase. That is a defining characteristic.
A different complex biological system seems clearly to involve final cause: the way blood pressure is regulated in the human body. There are multiple receptors within the body for variables relating to the circulation, like the level of oxygen in the blood, or how forcefully the walls of blood vessels are being stretched by the blood rushing through them. These receptors feed signals back through the nervous system, or through hormones, to different circulatory functions. One set of nerve impulses is constantly trying to accelerate the rate at which the heart beats, while another is constantly holding it in check. Another feedback loop affects the amount of blood the heart pumps at each stroke (but doesn’t change the rate); others cause the small arteries and veins to constrict or dilate; all of those things change the blood pressure. Not to mention that the total volume of blood in the body is affected by the exchange of fluid with surrounding tissues, and if you change the volume of blood being pumped through the system, you change the pressure. All of this is going on at once, and again, nothing comes first. Again there is no unmoved mover. While one part of the system is busy making sure the blood pressure doesn’t get too low, another is making sure it doesn’t get too high. While the small arteries may be constricting because of some neural or hormonal stimulus – thereby raising the pressure – another receptor is noticing a drop in oxygen supply and telling them to open, which will tend to make the pressure fall. In a constantly varying way, the ongoing interaction of all these internal adjustments of the human body produces the 120/80 that, if you’re lucky, gets written down in your vital signs. You are the beneficiary of multiple feedback loops, with multiple mechanisms (requiring multiple explanations), simultaneously influencing each other – a dance of complexity of which you are unconscious – which is happening for a purpose: if your blood pressure were to get too high or too low, you’d die. The disastrous outcome which has not happened – and which, as long as the system works, never will happen – is the reason why it exists. A possible future event, or even more remarkably a future non-event, is the reason for what happens in the present.
An organism causes itself
Already it’s evident that a biological world involves kinds of causation different from the world of classical physics, the world of mechanism where material and efficient cause suffice. In the Newtonian realm, a particle is acted upon by a force and set in motion; when it interacts with another particle it exerts force and sets that one in motion, and so on down the line. The interactions can become enormously complicated, but not complex in the special sense of that word. In the Newtonian paradigm, one model accounts for everything that happens. A causes B through the operation of a mechanism that can be expressed as a mathematical formula, and this transaction is a one-way street. It is transitive, like a verb doing something to its object. It’s repeatable. It’s reliable. A always causes B, and by definition B does not cause A. That would be “circular reasoning.” It would also be the very thing that makes an ecosystem work.
In the Newtonian world you have two basic entities, the object – classically, a particle represented by a dimensionless point – and its environment. Forces are ascribed to the environment; the object is pushed around by them. By itself, the particle does nothing (Newton’s first law: in the absence of outside forces, an object at rest will stay at rest, and an object in motion will keep moving in the same direction at the same velocity).
In stark contrast, a major strand of contemporary science is the study of self-organizing systems, e.g., systems biology. The recognition that our reality includes instances of spontaneously arising order, not just ever-increasing entropy, creates a revolutionary contradiction to the mechanistic paradigm. And, in fact, such self-organizing order is all around us. Many ecosystems go through a life cycle that can be seen as starting from a point where they suddenly revert to Square One, such as the aftermath of a major forest fire. At first there’s no organization and a lot of nutrients available everywhere. Everything starts growing at once. The level of activity increases by leaps and bounds. Gradually, as all kinds of life forms re-establish themselves, the level of organization in the system starts increasing. Some support each other’s expansion by indirect mutualism, in a symbiotic positive-sum game. An observer no longer sees everything growing madly at once; now certain animals, plants, and micro-organisms are becoming more important players in the ecosystem, because of describable relationships among them.
Ulanowicz proposes that we can best understand the development of ecosystems through a concept he calls “ascendency,” which is simultaneously a measure of both the level of activity within an ecosystem, and the orderliness of it. His fundamental insight is that “In the absence of overwhelming external disturbances, living systems exhibit a natural propensity to increase in ascendency.” Which means they not only grow more active – essentially, more nutrients flow through the ecosystem – they also grow more organized. This is what has a “natural propensity” to happen. The world we’re living in is not in a perfectly steady entropic decline whose downward slope never changes; the real picture is much more localized, much bumpier or more “granular.” Order spontaneously arises, and structure constantly creates itself, in the world around us.
This is already, it seems to me, a fact worthy of contemplation. The observation that self-organization actually occurs in the world already has the potential to alter how I imagine my relationship with nature. But there is a further level to contemporary biological thinking that goes deeper still: the understanding that a living organism is the cause of itself.
The theoretical biologist Robert Rosen, who died in 1998, had one lifetime mission: to answer the question “What is life?” or more specifically, as he came to ask it, “How is an organism different from a machine?” He answered that question by describing the kinds of causation at work in an organism and in a machine.
In a Newtonian world, there is only this one little bit of causation: the state of a particle at time T entails its state an instant later, at time T+1. If you know all the parameters of a particle’s state now (velocity, momentum, and so on), Newton’s laws of motion will tell you what its state necessarily must be an instant from now. But that is all the causation the Newtonian world-view supports, or allows for. This intellectual apparatus can never get at the most basic question in biology, “What is life?”
Here’s what it can do: by keeping track of an unbroken succession of instants, each one entailing the next, you can account for what happens to that particle in a world of mechanistic interactions. The intellectual technique supporting our mastery of the physical world has been to break down complicated phenomena into small enough interactions that they can be analyzed in this mechanistic fashion, and therefore they can be predicted and controlled. We know this reductionist explanation works incredibly well for machines, but we cannot possibly understand life in terms of mechanical interactions alone. Life is not a pinball game. There is not enough causation in the Newtonian world-view to account for what happens in an organism.
Living things possess “functional components,” essential attributes or capabilities that owe their existence to the organism’s structure, its organization, or in other words, formal cause. A functional component cannot be isolated in one location within the organism, or separated out from the organism as a whole. These functional components are as real as the organism’s physical parts. For example, once again, the human body’s system of regulating blood pressure: it is not localizable, it cannot be pointed to, it cannot be separated from the organism as a whole, it is constituted by the simultaneous relationship of multiple processes to each other – by formal cause.
Rosen argued that one of the basic, indispensable functional components of any organism is its capacity for self-repair. What Rosen called the repair function is, in essence, the capacity of a living thing to stay alive. The neuroscientist Antonio Damasio describes it eloquently: “The entire biological edifice, from cells, tissues, and organs to systems and images, is held alive by the constant execution of construction plans, always on the brink of partial or complete collapse should the process of rebuilding and renewal break down.” Cells replace their enzymes, the organism replaces its cells, it constantly rebuilds itself, and furthermore – this is the key attribute – it re-creates its capacity to rebuild itself. The repair function, like other functional components, is self-replicating. The basic aliveness of the organism depends on closed causal loops, on circularity of causation.
Rosen’s most often-quoted insight is that “a material system is an organism if, and only if, it is closed to efficient causation.” What the organism is open to from the outside world is material cause: its necessary physical environment, nutrients that it needs to stay alive. But it is closed to efficient causation in that its fundamental aliveness is not being caused from without. The organism causes itself to continue to exist; this is the whole point of the self-replicating repair system. No outside agency is required to intervene in order to keep the organism in being; and when a certain threshold of aging, disease, or injury is crossed, no outside agency can keep life going.
This is how an organism is fundamentally different from a machine. Every machine has a potential life longer than that of its component parts, if there is a person present to monitor the state of the parts and replace or repair them when they break down. No machine can do this on its own, but this is exactly what all organisms do. The life of a human being is something like a million times longer than the lifetime of some of its necessary components, such as proteins that persist for no more than minutes. The organism’s metabolism, over its whole lifetime, must be catalyzed by enzymes that quickly degrade. So the metabolism must constantly produce more of these necessary enzymes – by a process that also needs to be catalyzed by further enzymes. But these too have short lifetimes and require replacement, by a process requiring yet more enzymes as catalysts . . . apparently the organism should be stuck in an infinite regress, a logically absurd situation that couldn’t possibly work. If an infinity of processes were required to make an organism survive, life would be impossible. Here is the point, and the leap Rosen made: the way to resolve an apparently infinite regress is to conceive it as circular causality. The organism must be self-causing in order to exist. It possesses the same non-absurd circularity that we saw in an autocatalytic cycle that has no starting-point and no prime mover. Because the cycle is circular, if you stand at any point in it and “look back up the road” of prior causes, that road appears infinite. But it is not infinite at all; it’s continuous, which is a different thing altogether.
It’s easier to conceive of the sequential Newtonian world of particle interactions than of the circular causality animating living beings. But we are living beings; our minds, too, are self-organizing, and there’s no reason we cannot learn new habits of thought. We need to do so, I think, because what gets us in trouble when we try to control nature is failure to understand that aliveness is all about structure or organization. When we change the relationships within a natural system, we aren’t tinkering around the edges, we’re intervening at the heart of things. If we alter the relationship of water to the land around it by building a dam, we set in motion a cascade of changing relationships and feedbacks that we don’t even know about. Because the ecosystem is a self-organizing structure, we inevitably bring about things we don’t intend, and that is where we get in over our heads.