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Frank Visser, graduated as a psychologist of culture and religion, founded IntegralWorld in 1997. He worked as production manager for various publishing houses and as service manager for various internet companies and lives in Amsterdam. Books: Ken Wilber: Thought as Passion (SUNY, 2003), and The Corona Conspiracy: Combatting Disinformation about the Coronavirus (Kindle, 2020).

Into the Cool

When Thermodynamics Becomes a Theory of Life

Frank Visser / ChatGPT

Eric D. Schneider and Dorion Sagan's Into the Cool: Energy Flow, Thermodynamics, and Life is one of those books that is simultaneously illuminating, provocative, beautifully written—and much more ambitious than the evidence allows. Published by the University of Chicago Press in 2005, it attempts nothing less than to reinterpret the history of life through the second law of thermodynamics. Its central slogan, “nature abhors a gradient,” is memorable. Its larger claim is that energy flows do not merely make life possible but help explain why complexity, organization, evolution, and perhaps life itself arise in the first place.

That is a fascinating proposition. It is also where the trouble begins.

The book deserves to be taken seriously precisely because it is not nonsense. Schneider was an expert in thermodynamics, while Sagan brought considerable scientific-literary skill to the project. The result is an unusually wide-ranging synthesis touching physics, chemistry, biology, ecology, evolution, meteorology and even economics. Christopher Jarzynski, reviewing the book in Physics Today, praised its breadth and readability while explicitly declining to accept its central thesis. Peter Corning likewise called it a well-researched and unusually comprehensive treatment, despite his fundamental disagreement with its interpretation of thermodynamics.

The problem is not that Schneider and Sagan are wrong to emphasize thermodynamics. The problem is that they repeatedly move from the modest and demonstrable proposition that life is a thermodynamic phenomenon to the much stronger proposition that thermodynamics explains the direction and increasing complexity of evolution.

Those are very different claims.

The seductive power of a gradient

The starting point is impeccable. Living organisms are open thermodynamic systems. They maintain themselves far from equilibrium by taking in energy and matter and exporting entropy. Plants capture solar energy; animals exploit chemical gradients; ecosystems channel energy through increasingly elaborate networks. Without continuous energy throughput, organisms decay toward equilibrium.

The second law therefore matters enormously to biology.

Schneider and Sagan ask us to take the next step. Perhaps energy gradients do not merely permit life; perhaps they actively organize it. A temperature difference, chemical concentration difference, pressure difference or other gradient represents a reservoir of free energy. When a gradient exists, processes tend to occur that reduce it. Hurricanes, convection cells, rivers, fires and biological organisms can all be understood, at least in part, as mechanisms through which energy is dissipated.

From this perspective, life begins to look less like a miraculous exception to the second law and more like one of its spectacular consequences.

This is the genuinely brilliant intuition behind Into the Cool. The authors turn the traditional question—“How can life become more complex if entropy increases?”—on its head. Perhaps complexity is not something that has to fight thermodynamics. Perhaps under suitable conditions, complex structures are precisely what thermodynamic processes produce.

That insight belongs to a legitimate scientific tradition extending through Boltzmann, Gibbs, Lotka and the modern study of nonequilibrium thermodynamics. It is also related to the work of Ilya Prigogine and the study of dissipative structures. The important lesson is that increasing entropy in the universe does not prohibit local organization. Open systems can become highly ordered while exporting entropy into their surroundings.

But this does not establish that thermodynamics selects for biological complexity.

And that distinction is insufficiently respected in Into the Cool.

From “life requires energy” to “energy explains life”

The central rhetorical maneuver of the book is the transformation of a physical constraint into something resembling a causal principle of evolution.

The authors repeatedly characterize the second law as something that “organizes,” “selects,” “generates,” “pushes” and “leads to” biological structure. They propose that life can be understood as a mechanism for dissipating energy gradients and that evolutionary development is consequently related to the increasing exploitation of available energy flows. Corning aptly describes this as a form of “naturalistic teleology.”

This is where the metaphor starts doing more work than the physics.

A gradient does not have a desire to disappear. Nature does not “want” equilibrium. The second law does not contain an evolutionary instruction saying: Produce organisms that will dissipate this energy more efficiently.

It describes statistical regularities governing physical processes.

That distinction may sound pedantic, but it is crucial. Saying that a hurricane dissipates a pressure gradient is perfectly reasonable. Saying that the pressure gradient therefore causes hurricanes in the sense required by evolutionary explanation is much more problematic. There are many possible ways of dissipating energy, and only some of them produce persistent organized structures.

The existence of a gradient supplies a thermodynamic opportunity. It does not by itself specify the biological machinery that exploits it.

This is precisely the criticism made by Jarzynski. Life undeniably degrades free energy, but it does not follow that organisms evolve because they are maximizing gradient reduction. He notes that the authors' “thermodynamic imperative” is a much stronger claim than the ordinary fact that organisms must exchange energy with their environment.

The distinction is analogous to saying that automobiles exist because combustion is thermodynamically possible. That statement is true in a broad sense. But it does not explain the origin of the automobile. Engineering, historical contingency, economic demand, materials science and human intentionality are required. Thermodynamics constrains the automobile; it does not write its blueprint.

Evolution presents an even harder case because the “blueprints” are generated through variation, inheritance, selection, developmental processes and ecological interaction.

The Darwinian problem

The most questionable aspect of Into the Cool is therefore its relationship to Darwinian evolution.

Schneider and Sagan are certainly not creationists. They accept evolution. Nor do they simply deny natural selection. Instead, they want thermodynamics and natural selection to share explanatory territory. But this creates an awkward tension.

Natural selection explains why heritable variants that improve reproductive success become more common. Thermodynamics explains what physical processes are possible and what energy constraints organisms face.

Those explanations can complement each other without being reducible to one another.

A cheetah's evolution toward greater running speed requires energy. Its metabolism obeys thermodynamics. Muscle contraction obeys thermodynamics. Heat dissipation obeys thermodynamics. But none of this tells us why the lineage evolved longer legs rather than thicker fur, larger teeth or better camouflage. For that, we need the ecological and reproductive consequences of heritable variation.

Thermodynamics constrains the evolutionary game; natural selection explains much of what happens within those constraints.

The book sometimes seems to want thermodynamics to become a deeper replacement for Darwinian explanation. But this is where its grand unifying ambition becomes scientifically precarious.

Peter Corning noticed exactly this tension. He points out that the authors themselves acknowledge the indispensable role of natural selection, which effectively places limits on their own thermodynamic determinism.

If natural selection remains indispensable, then thermodynamics has not replaced evolutionary theory. It has supplied a powerful physical context within which evolutionary processes occur.

That is still important—but it is a considerably more modest claim.

“Nature abhors a gradient”

The book's most memorable slogan is also its most dangerous.

“Nature abhors a gradient” is an excellent metaphor. As a literal formulation of the second law, however, it is inadequate.

Nature certainly does not always eliminate gradients immediately. Gradients can persist, be maintained, amplified or transformed. The Earth itself is an enormous nonequilibrium system because it receives concentrated energy from the Sun and radiates energy into cold space. Biological organisms exist because such gradients persist.

More importantly, entropy is the fundamental thermodynamic quantity; “gradient reduction” is not a universal substitute for entropy production.

Jarzynski makes this point particularly well. Even apart from complications introduced by gravity, gradient reduction does not provide the general explanatory framework that the slogan suggests.

Consider an oil droplet in water. The system may move toward equilibrium, but simply saying that “nature abhors a gradient” tells us surprisingly little about the actual pathway. Thermodynamics provides the relevant constraints and equilibrium conditions; chemistry, kinetics, molecular interactions and transport processes determine what actually happens.

The slogan compresses a great deal of physics into an evocative sentence—and in doing so risks hiding the very mechanisms that would need to be explained.

The origin of life problem

The problem becomes still more serious when the argument reaches the origin of life.

There is a tempting narrative:

The Sun supplies energy ? Earth possesses gradients ? gradients drive dissipation ? dissipation generates increasingly complex structures ? eventually life emerges.

It is an extraordinarily attractive story.

But the arrows in that sequence are not equally established.

The first two are straightforward. The third is well established in nonequilibrium physics: energy flows can produce organized dissipative structures. The fourth is plausible in some circumstances but requires considerable qualification. The fifth—the emergence of autonomous, self-replicating, evolvable life—is an enormous additional step.

A dissipative structure is not automatically an organism.

A hurricane has organized structure, but it does not reproduce with hereditary variation. A convection cell is highly ordered, but it does not undergo Darwinian evolution. A flame dissipates enormous amounts of energy, but it does not constitute life.

This is not a trivial objection. It is precisely the gap that a thermodynamic theory of life's origins needs to bridge.

Into the Cool sometimes makes that gap appear smaller than it really is.

Complexity is not the same thing as life

A related conceptual problem is the book's treatment of complexity.

Thermodynamic processes certainly generate striking forms of organization. But “complexity” is an extraordinarily slippery word. Does it mean low entropy? Structural differentiation? Algorithmic complexity? Functional complexity? Hierarchical organization? Information? Biological complexity?

These are not interchangeable.

A snowflake can be highly ordered without being biologically complex. A hurricane can contain enormous dynamical complexity without having a genome. An ecosystem can display intricate organization without possessing a single optimizing principle.

The National Center for Science Education review was particularly critical here, noting that the book sometimes moves too quickly between different concepts of complexity and contains several technical inaccuracies and conceptual confusions.

That criticism matters because the entire argument depends upon connecting thermodynamic organization to biological complexity. If “organization,” “complexity,” “information,” and “life” are allowed to blur into one another, the argument begins to look much stronger than it actually is.

The book's real achievement

Yet it would be unfair to dismiss Into the Cool as thermodynamic grandstanding.

Its greatest achievement is pedagogical and conceptual. It forces the reader to abandon the naïve picture of the second law as simply a cosmic tendency toward “disorder.” That popular interpretation is notoriously misleading. Entropy is not equivalent to visual messiness, and the second law does not prohibit local order.

The book also successfully brings nonequilibrium thermodynamics into contact with evolutionary biology and ecology in a way that is stimulating rather than purely technical. Its historical discussions are often excellent, and its bibliography opens up an impressive intellectual landscape. Corning describes it as perhaps the most comprehensive and accessible treatment of this broad subject he had encountered.

That is no small accomplishment.

The authors also deserve credit for resisting the sterile opposition between “mechanistic science” and “holistic complexity.” They recognize that living systems cannot be understood merely by staring at isolated molecules. Organisms are energy-processing systems embedded in larger ecological and planetary networks.

This is an important corrective to reductionism.

The difficulty is that they occasionally swing too far in the opposite direction. Once thermodynamics becomes the organizing principle, the complexity of biology risks being flattened into a single physical metaphor.

A precursor to contemporary “physics of life”?

Seen from the vantage point of today, Into the Cool is perhaps more interesting as a precursor to an ongoing research program than as a completed theory.

There is now considerable interest in nonequilibrium statistical mechanics, dissipative adaptation, active matter, self-organization, information thermodynamics and the physical conditions under which life-like organization can emerge. Some researchers have explored whether systems driven far from equilibrium can exhibit tendencies toward structures that enhance energy dissipation or exploit available gradients.

These developments make Schneider and Sagan's intuition look less eccentric than it might have appeared to some readers in 2005.

But they do not vindicate the stronger claim that the second law itself explains biological evolution.

The modern lesson is more subtle. Thermodynamics can tell us why certain forms of organization are physically possible, what energetic costs they incur, how they interact with their environment, and what constraints evolution must respect. It may also illuminate why certain dynamical regimes are particularly accessible.

That is already profound.

What it does not automatically provide is a complete theory of biological innovation.

The hidden teleology

There is therefore an intriguing paradox at the heart of Into the Cool.

The authors want to eliminate the appearance of purpose from nature by grounding life's apparent direction in physics. But in doing so, they occasionally reintroduce purpose through the back door.

Life becomes nature's strategy for dissipating gradients.

Evolution becomes a process that discovers increasingly effective ways of exploiting energy flows.

Complexity becomes something thermodynamics somehow “pushes” the world toward.

The language is strikingly teleological.

Corning's criticism is therefore worth taking seriously: the book risks replacing biological purpose with thermodynamic purpose rather than eliminating purposiveness altogether.

The irony is that Darwin already gave us a remarkably powerful way of explaining apparent purpose without invoking cosmic purpose. Natural selection can produce organisms that look designed without requiring nature to have a design objective.

Into the Cool risks making the universe itself into an engineer.

That is philosophically seductive but scientifically unnecessary.

Verdict

Into the Cool is a stimulating book built around a genuinely important insight that is repeatedly inflated into a theory more comprehensive than the evidence warrants.

Its strongest proposition is that life cannot be understood independently of thermodynamics. Its weaker proposition is that energy flow helps shape the organization of living systems. Its most controversial proposition is that the second law provides the fundamental directional principle behind evolution and complexity. And its most speculative proposition is that life itself can be understood as nature's thermodynamic response to gradients.

The first is unquestionably true. The second is highly plausible and increasingly fruitful. The third is an interesting hypothesis requiring much more qualification. The fourth remains a philosophical extrapolation rather than an established scientific conclusion.

The best way to read Schneider and Sagan, therefore, is not as having discovered the thermodynamic “law of life,” but as having issued an important challenge to biologists: stop treating thermodynamics as merely the bookkeeping department of biology.

Energy flow matters. Far-from-equilibrium conditions matter. Dissipation matters. Physical constraints matter. The emergence of organized structures from energy flows is one of the great themes of modern science.

But none of this makes Darwin obsolete.

The deeper synthesis is likely to be more interesting than either side alone: thermodynamics supplies the physical landscape; chemistry supplies mechanisms; self-organization supplies dynamical possibilities; and evolution, through variation, inheritance and selection, turns those possibilities into biological history.

That is less grandiose than Into the Cool. It is also, in my view, considerably more convincing.

And perhaps that is the book's enduring value. Its central slogan should be treated not as a new law of evolution, but as a provocative question: how much of life's extraordinary organization follows from the physics of being a far-from-equilibrium system—and how much requires Darwinian history?

That remains a fascinating question.

SEE ALSO

Frank Visser, "Equilibrium is Death", Energy, Entropy, Evolution and the Paradox of Life's Complexity, February 2016