I believe this book has the potential to change--and perhaps revolutionize--scientific thinking in a great many areas. Deacon presents a theory of "emergent dynamics" to explain how the emergence of higher-level processes from simpler physical processes changes causal dynamics in surprising and dramatic ways. His main objective is to show that "ententional" phenomena (function, information, meaning, reference, representation, agency, purpose, sentience, and value) have a legitimate place in scientific explanation once they are properly understood. Accomplishing that would overcome an enormous divide in modern thought since Descartes, with physical scientists tending to eliminate or marginalize these phenomena because they can't fit them into their mechanistic models, and more phenomenological thinkers insisting on them as essential aspects of our human experience, although not being able to explain how they can exist in a material world. In the course of presenting his solution to that problem, Deacon makes major contributions to the understanding of causality, emergence, organisms, evolution, work, information, emotion, and consciousness.
Fundamental to Deacon's argument is a distinction between "orthograde" changes, which occur spontaneously without external interference, and "contragrade" changes, which must be extrinsically forced. Contragrade changes correspond to Aristotle's efficient causality, the usual causality assumed in mechanistic explanation. Such explanation tends to overlook orthograde change and the more subtle formal and/or final causality it involves. Deacon understands form as a constraint on the possible states of a system, a definition that avoids both extreme realism (general forms existing prior to particulars, as in Platonism) and extreme nominalism (forms existing only in the minds of observers). Defined as constraint, form refers in a way to what isn't physically present, and yet what has definite causal consequences. Final causality is the ability of a synergistic system of forms to become its own cause by perpetuating itself.
Deacon distinguishes three levels of dynamic process, each with its own orthograde tendency. A "homeodynamic" process spontaneously reduces a system's constraints to their minimum, as exemplified by the increase in entropy described by the second law of thermodynamics. Although a large number of objects interacting in a system exert efficient causality on one another, an increase in entropy arises from the statistical form of the system as a whole, in which disordered macro-states far outnumber ordered states; in that sense the homeodynamic process exhibits formal causality.
When systems in different thermodynamic states encounter each other, they exert a contragrade influence, as when a hotter system encounters a colder one, so that each is moved away from the equilibrium it otherwise would have had. The second level of dynamic process, "morphodynamic," emerges when the flow of "energy" across such a gradient is constrained so as to generate order; it is a process of form generating more form. The crystalline form of a falling snowflake places constraint on where additional molecules will form when it freezes some of the water molecules it encounters in the air, so its form generates more form over its unique interactional history. Surprisingly then, a higher-level order-building process emerges out of the lower-level tendency toward thermodynamic equilibrium, one illustration of how emergence transforms causal dynamics. Morphodynamic processes occur only rarely and fleetingly in the inorganic world, but they are essential to the organic world. They rely on the thermodynamic foundation of radiation from the Sun to the Earth, constrained and put to the work of building bodies.
Organisms depend on a number of morphodynamic, order-building processes, each inducing contragrade changes in others, but in a synergistic way. One process creates a condition favorable to another, so that it can continue rather than wind down by destroying the conditions that gave rise to it. A self-assembly process similar to crystal formation can build a cellular wall, providing a protected space for an autocatalytic process that creates many molecules of the same kind, providing a continued supply of material for self-assembly. This kind of synergy generates Deacon's third level of dynamic process, called "teleodynamic" or end-directed, in which the system's orthograde tendency is to perpetuate itself by sustaining its closely coordinated morphodynamic processes. This gives organisms a kind of closure from external processes, creating a distinct self, able to act on its own behalf in its environment in order to sustain itself.
Purely bottom-up explanation, trying to find the causes of the organism's behavior at lower levels, will be insufficient here. The lower-level physiological details can vary greatly, as long as the macro-level constraints are perpetuated. And the component processes are affected by the synergistic relationships in which they participate, so they can't be understood simply as independent causes. This is also relevant to the understanding of genetic information, whose meaning is not intrinsic but dependent on the teleodynamic context in which it is used. That's part of the problem of seeing the organism as a machine running a genetic "program."
In animals with brains, a second-order self can emerge, which we call "consciousness". This is a more specialized teleodynamic process contributing to the more general teleodynamics of the organism. Like any teleodynamic process, it is thermodynamically driven (it takes energy to feel and think) and emergent from morphodynamic synergies (interdependencies among order-generating processes within the vast neural network of the brain). And like any teleodynamic process, it is inherently self-sustaining. But what does it do for the body? Deacon describes it as a representational process that interprets the organisms's own teleodynamic tendency. I take that to mean that this process maintains a normative model of what the animal is trying to do, allowing it to anticipate opportunities and threats rather than just reacting to them. At the risk of putting words in Deacon's mouth, I would conclude that it is purposive in a double sense, having its own purpose of sustaining itself so that it can give purpose (direction) to the organism as it tries to sustain itself. Like any teleodynamic process, it performs work on what is "other" to itself, but in this case what is other includes other processes within the same body. Deacon makes the intriguing suggestion that the work done to mobilize the body to respond to favorable or unfavorable contingencies is experienced as emotion.
This perspective leads more naturally than any other I'm aware of to an understanding of human beings as thinking, feeling, and active free agents. But as Deacon says, freedom has to be understood not as freedom from causality, but freedom to exercise causal power, including some power over ourselves!
Obviously Deacon takes a dim view of cognitive science and neuroscience models that reduce thought to mechanical computation or relegate consciousness to the role of passive spectator to the brain's bottom-up causal activity. Mind isn't a ghostly immaterial entity existing beyond causality, but neither is it causally epiphenomenal (inconsequential). It is a dynamic process that evolved because of its function in sustaining and coordinating bodily activity in a very subtle way, through the perpetuation of constraint. Since mechanistic models only consider the extrinsic force exerted on one part by another in a deterministic system, they overlook the spontaneous propagation and self-persistence of constraints that organize our world while leaving it open to further organization.
I do have one reservation about Deacon's position, and that is that I'm not as sure as he is that teleodynamic process was absent for most of the universe's history. His description of teleodynamics reminded me of physicist David Bohm's concept of reciprocal causation, which he intends as a universal principle. I understand why Deacon wants to limit the discussion to living things, and I find his account of teleodynamics there persuasive, but perhaps he closes the door a little too firmly against the possibility of a self-sustaining process on a deeper level. I wonder what Aristotle would make of that.
Overall, I recommend this book very highly and hope that it will be widely read. Anyone who wants to think about human beings scientifically without reducing them to robots (or "golems") will benefit from it. In the Machine Age, we modeled our relationship to nature as a relationship of "man to machine," which ultimately forced us to regard ourselves as machines in order to include ourselves in nature. So the model became machinery controlled by machinery, with no place for consciousness, purpose, feeling or value. Now it's time to recover our respect for nature's purposes, as well as our own self-respect. As Deacon ends the book, "Even as our scientific tools have given us mastery over so much of the physical world around and within us, they have at the same time alienated us from these same realms. It is time to find our way home."