diff --git a/elements/neuron/appunti/2026-07-06-logic-principles-of-the-expresion_v5.md b/elements/neuron/appunti/2026-07-06-logic-principles-of-the-expresion_v5.md
index 9aeeb13..a0f8f43 100644
--- a/elements/neuron/appunti/2026-07-06-logic-principles-of-the-expresion_v5.md
+++ b/elements/neuron/appunti/2026-07-06-logic-principles-of-the-expresion_v5.md
@@ -118,6 +118,21 @@ fast and slow are same-order coupled, it never recurs (irreversible ratchet), an
 incommensurable. The methods do not fail by bad luck; each needs the stable, reusable structure that
 "the specification is continuously rewritten by its own running" abolishes.
 
+**And here the exponential appears — not as the obstruction, but as its price.** Suppose you refuse
+all of the above and insist on simulating anyway. To simulate *is* to fix a structure: a simulation
+is a set of variables updated by fixed rules, and you cannot write the loop without committing to
+what the variables are. But the real structure changes every night. So you face a forced choice.
+Freeze *one* structure and you have committed to a single branch — one accidental history, a
+measure-zero sample of a thing that is not a distribution. Stay faithful while keeping a fixed
+substrate and you must instead carry *every* structure the system might occupy as an enumerated set —
+and that set multiplies each night, growing exponentially in the number of nights, of changing
+dimension, non-factorable. This exponential is not a property of the model; the model never
+enumerates, it simply becomes one structure. The exponential is the shadow the fluid, self-rewriting
+model casts on a fixed substrate — it arises *if and only if* you demand the stable structure that
+simulation requires. The need for stable structure is what converts self-rewriting into
+exponential enumeration; drop the demand and the exponential vanishes, leaving only a physics living
+one history.
+
 **Three concrete faces of the obstruction.** *The foreclosed synapse:* a synapse pruned on night 3
 is gone; a pattern that would have used it on night 50 breaks at that link and cannot replay, so its
 downstream components lose participation and drift toward pruning too — one cheap early pruning