The configuration [§7.8](<7.8 Life.md>) defines (closed self-producing recursion coupled to sustained energy throughput) is composed of three structural subsystems, each necessary, with joint sufficiency the structurally predicted open empirical frontier [§7.8.1](<7.8.1 What is Disputed.md>) names. Each is a minimum constituent any realization of life must instantiate, regardless of substrate: the structural account is committed to the form, not to the chemistry.

*The production network.* The closure side of life is a network of components that produce the components that maintain the network. Maturana and Varela -(Humberto R. Maturana, Francisco J. Varela, 1980) named the structure *autopoiesis*: a system organized as a network of processes of production whose outputs include the very processes that produced them, and whose collective activity reconstitutes the system that does the producing. Kauffman -(Stuart A. Kauffman, 1986); -(Stuart A. Kauffman, 1993) described the same closure dimension chemically as an *autocatalytic set*: a set of catalysts in which every member is produced by some reaction within the set, so the set as a whole catalyzes its own continued existence. The two formulations name the same structural fact at different abstractions: a network is closed when its production cycles back to itself.

Closure is what distinguishes the configuration from a flame or a hurricane ([§7.8](<7.8 Life.md>)). Dissipative structures channel energy without producing the components that channel it; the autocatalytic network produces its own producers. The network is necessarily *bounded* (components must remain in proximity to interact) but the boundary need not be a phospholipid membrane. Any persistent constraint that holds the production network together against diffusion will do: a mineral pore at a hydrothermal vent, a coacervate droplet (a liquid droplet that spontaneously separates from a surrounding aqueous solution because the macromolecules inside it associate more strongly with one another than with water, concentrating reactive species without requiring a membrane), a vesicle, a cell wall. Boundary type is parochial; boundedness is constitutive.

*The energy gradient.* The throughput side is the configuration's coupling to a sustained energy gradient that the network dissipates through itself. Schrödinger -(Schrödinger, E., 1944) named what life feeds on as *negative entropy*: ordered inputs absorbed, disordered outputs released. Prigogine and Nicolis -(Prigogine, I., and G. Nicolis, 1977) gave the result thermodynamic teeth; the fluctuation theorems of Jarzynski -(Jarzynski, C., 1997) and Crooks -(Crooks, G. E., 1999) supply the formal nonequilibrium-thermodynamics foundations on which contemporary dissipation-and-self-organization arguments rest. Configurations capable of self-replication are favored outcomes in systems strongly coupled to sustained gradients (England -(England, J. L., 2013) offers one specific articulation of the claim; [§7.8.1](<7.8.1 What is Disputed.md>), [§7.8.3](<7.8.3 What is Predicted.md>)). The gradient does not have to be of any particular kind (chemical, thermal, photic, redox) but it has to be *sustained* over the timescales the closure requires to maintain itself. A transient gradient will fuel a flame; only a sustained gradient will fuel a recursion.

The bonds the gradient acts on are themselves nothing new. Covalent, hydrogen, ionic, and dispersive interactions are all expressions of the electromagnetic force already constitutive of Substance (Linus Pauling, 1939); the strong and weak nuclear forces operate at sub-atomic scale, gravity at planetary scale and above, and chemistry (including the chemistry of life) runs entirely on electromagnetic interactions. Life therefore introduces no new force. What it introduces is a *configuration* in which a sustained gradient is enrolled to maintain improbable arrangements of interactions that already exist.

A further temporal asymmetry constrains the *first* gradient. At the moment of the first closure, no prior life exists to be consumed, so the first gradient must be non-biological, and among non-biological gradients, photosynthesis is ruled out by the molecular machinery it requires (which is itself a downstream evolutionary product). The first gradient is therefore structurally favored to be chemical, redox couples (paired oxidation–reduction half-reactions, in which one species loses electrons and another gains them, releasing free energy that can be enrolled in downstream chemistry) at sites of sustained geochemical disequilibrium, given that the alternatives the literature has surveyed all require evolved molecular machinery the first closure could not have inherited. The non-biological-source constraint is strict; the redox/chemoautotrophic identification is the abductive best fit, matching the parent [§7.8](<7.8 Life.md>) calibration. Subsequent life can run on biological gradients (heterotrophy, parasitism) and on photic gradients once photosynthetic machinery has evolved; the first cannot.

The coupling is structural. The production network does not merely sit in the gradient; it routes the gradient through itself, transducing the input form into work that maintains the network's own production. The energy is *enrolled* in the closure rather than passing alongside it. This is what distinguishes life from any dissipative structure: the energy that flows through life flows through life *because* life uses that flow to keep itself producing itself.

*The heritable specification.* The third subsystem is heritable information: a template that specifies the components of the production network with sufficient fidelity that the network can be replicated. Without heritable specification, a closed network can persist for as long as its components hold together, but the closure cannot propagate beyond a single instance, and selection cannot operate. Eigen's hypercycle -(Eigen, M., 1971) and Gánti's chemoton -(Tibor Gánti, 2003) both identify the information subsystem as a third coupled cycle running alongside the metabolic and membrane cycles, each cycle dependent on the others, none reducible to the rest. Joyce's NASA definition -(Joyce, G. F., 1994) names the same component when it requires Darwinian evolution: heritable variation under selection presupposes a template that can vary and be inherited.

What the information subsystem adds structurally is the ability of the closure to *outlast its instantiation*. A single closed network is alive while it persists; a network with heritable specification is alive across lineages. The framework's structural-necessity claim (that the trajectory deepens given enough time, [§7.8](<7.8 Life.md>)) depends on the information subsystem, because deepening requires variation under selection across generations, which requires templates that copy with error.

A further structural constraint is forced by the temporal asymmetry of the first closure. The heritable subsystem requires both a template and the catalysis that copies it; in modern life these are separated into DNA (template) and protein enzymes (catalysis). But the protein machinery is itself a product of templated synthesis: every catalyst in modern protein synthesis is itself templated. The first heritable system cannot work this way: there are no specialized catalysts yet, because specialized catalysts are downstream products of templated synthesis. The first heritable medium must therefore combine both functions in a single molecular class. This is the *catalysis-template duality* the heritable subsystem must satisfy at the origin. The empirical instantiation on Earth is the RNA world (Walter Gilbert, 1986); (Joyce, G. F., 2002): RNA folds into 3D shapes that catalyze reactions (ribozymes) while also serving as readable sequence templates. Whether RNA specifically is the answer for life elsewhere is an empirical question, other duality-capable polymers have been investigated as candidates (PNA, TNA, glycol nucleic acids; Eschenmoser; Nielsen), but the structural fact is the duality requirement, not the specific molecule that satisfies it.

*Three coupled cycles.* The synthesis is Gánti's: life is the simultaneous operation of three coupled cycles, metabolic (autocatalytic production), membrane (self-maintained boundary), and informational (template replication), none of which can run alone. Remove the metabolism and the membrane and template have no source of components; remove the membrane and the metabolism dissipates and the template diffuses; remove the template and the closure persists but does not propagate. The chemoton is the minimum structural decomposition of what [§7.8](<7.8 Life.md>) names as one configuration. Kauffman's autocatalytic sets, Maturana and Varela's autopoiesis, Eigen's hypercycles, Deacon's autogen -(Terrence W. Deacon, 2012), and the NASA–Joyce definition each foreground one or two of these cycles; the structural account holds that all three are required, and that any realization of life (terrestrial or otherwise) will be decomposable into these three subsystems regardless of the chemistry that implements them.

This is the structural anatomy. [§7.8.3](<7.8.3 What is Predicted.md>) traces the chain it predicts; [§7.8.4](<7.8.4 What is Confirmed.md>) reads it against the empirical literature.


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← [7.8.1 What is Disputed](<7.8.1 What is Disputed.md>) | [7.8.3 What is Predicted](<7.8.3 What is Predicted.md>) →
