Thin liquid films are commonly described through rupture, drainage, interfacial response, and stability vocabularies. This paper specifies a descriptive constraint on such vocabulary rather than proposing a new stabilizing mechanism. The constraint concerns the inferential route by which observed persistence is retrospectively organized as stability, closure, or completed equilibrium. Equilibrium and stability are retained as conventional labels within classical interface physics, not as names for a completed state already reached by the film. The Young–Laplace relation and interfacial mechanisms such as Marangoni elasticity remain essential physical references. The configuration at issue is the observed interval in which spherical form, thinning, fluctuation growth, rupture-readiness, drainage, and interfacial response remain adjacent without being reduced to a single stabilizing mechanism. The paper therefore distinguishes observed persistence from completed stability. Apparent persistence is not treated as illusory, but neither is it taken as proof that a stable basis has been established. Thin-film persistence remains describable only while form remains observable and collapse-related divergence remains unresolved. On that condition, persistence can be described without converting unresolved divergence into closure or completed equilibrium.
Tomoyuki Yorisuna (Thu,) studied this question.