**[[168_O2_Coherence-Primitive|O2]] (Coherence Primitive):** Coherence is an ontological primitive—the necessary organizing principle that makes information meaningful rather than noise. Coherence is not merely a property of information but an irreducible feature of reality that enables pattern, structure, and order.
Low entropy is a measure of coherence, not an explanation of it. Saying coherence is low entropy is like saying mass is kilograms—true but not reductive. The question is: why does the universe permit and exhibit low entropy states? Why do physical laws preserve certain structures against entropy increase? The existence of coherence-preserving dynamics is the primitive fact. Entropy is the measure; coherence is the phenomenon measured.
Scale-relativity doesn't undermine primitiveness. Information is also scale-relative (coarse-graining). The point is that at EVERY scale, there is a distinction between coherent and incoherent states. The primitive fact is that this distinction exists and matters physically. Thermodynamic laws are coherent—they constitute the macroscopic coherence. The hierarchy of coherences across scales is itself a coherent structure.
Evolution explains the INCREASE and OPTIMIZATION of coherence in biological systems. It does not explain why coherence is possible at all, why physics permits coherent structures, or why there's something to select from (initial coherent conditions). Evolution is a coherence-amplifying mechanism operating on a coherence-permitting substrate. The substrate's coherence is primitive.
Anthropic reasoning explains why we OBSERVE coherence but not why coherence EXISTS. The anthropic principle requires a space of possible universes, some coherent and some not, with observers necessarily in coherent ones. But what determines this space? Why are coherent universes possible? The possibility of coherence is the primitive fact; anthropic selection merely explains our location within it.
Decoherence transforms quantum coherence into classical correlation—it doesn't eliminate coherence but redistributes it. The universe's total coherence (quantum + classical) is conserved under unitary evolution. Decoherence explains the TRANSITION between coherence types, not the EXISTENCE of coherence. Moreover, the unitary evolution that leads to decoherence is itself coherent (deterministic, structured).
Second Law and Coherence Degradation:
Coherence naturally degrades in isolated systems. This makes coherence precious—it requires explanation and preservation.
Free Energy as Coherence Currency:
Free energy measures ability to do work = ability to maintain coherence. Living systems are free energy transducers maintaining coherence against entropy.
Low Entropy Initial Condition:
Penrose estimates initial entropy S_i \ll 10^{123} k_B (maximum). The Big Bang was extraordinarily coherent. This is the ultimate source of all subsequent structure.
Kolmogorov Coherence:
Fraction of string that is compressible. Random strings have C_K \approx 0; patterned strings have C_K > 0.
Incompressibility Theorem:
Most strings are incompressible (random). Compressible (coherent) strings are rare. Coherence is special, not default.